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    <link:label id="lab_ck0001710607_AuthorizedParticipantConcentrationRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_AuthorizedParticipantConcentrationRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Authorized Participant Concentration Risk Member</link:label>
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    <link:label id="lab_ck0001710607_BloombergU.S.AggregateBondIndexInceptionDate62921IndexMember_documentation_en-US" xlink:label="lab_ck0001710607_BloombergU.S.AggregateBondIndexInceptionDate62921IndexMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Bloomberg U.S. Aggregate Bond Index (Inception Date 6.29.21)</link:label>
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    <link:label id="lab_ck0001710607_PrepaymentAndExtensionRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_PrepaymentAndExtensionRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Prepayment And Extension Risk Member</link:label>
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    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ck0001710607_PrepaymentAndExtensionRiskMember" xlink:to="lab_ck0001710607_PrepaymentAndExtensionRiskMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ck0001710607_C000228610Member_label_en-US" xlink:label="lab_ck0001710607_C000228610Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">American Century Core Plus Income ETF Class</link:label>
    <link:label id="lab_ck0001710607_C000228610Member_documentation_en-US" xlink:label="lab_ck0001710607_C000228610Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">American Century Core Plus Income ETF Class, C000228610, ABND</link:label>
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    <link:label id="lab_ck0001710607_MarketTradingRiskMember_label_en-US" xlink:label="lab_ck0001710607_MarketTradingRiskMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Market Trading&#160;Risk Member</link:label>
    <link:label id="lab_ck0001710607_MarketTradingRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_MarketTradingRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Market Trading&#160;Risk Member</link:label>
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    <link:label id="lab_ck0001710607_MarketRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_MarketRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Market Risk Member</link:label>
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    <link:label id="lab_ck0001710607_BloombergU.S.13MonthTreasuryBillIndexInceptionDate31423IndexMember_documentation_en-US" xlink:label="lab_ck0001710607_BloombergU.S.13MonthTreasuryBillIndexInceptionDate31423IndexMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Bloomberg U.S. 1-3 Month Treasury Bill Index (Inception Date 3.14.23)</link:label>
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    <link:label id="lab_ck0001710607_InterestRateRisk1Member_documentation_en-US" xlink:label="lab_ck0001710607_InterestRateRisk1Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Interest Rate Risk1 Member</link:label>
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    <link:label id="lab_ck0001710607_C000241171Member_label_en-US" xlink:label="lab_ck0001710607_C000241171Member" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">American Century Ultrashort Income ETF Class</link:label>
    <link:label id="lab_ck0001710607_C000241171Member_documentation_en-US" xlink:label="lab_ck0001710607_C000241171Member" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">American Century Ultrashort Income ETF Class, C000241171, FUSI</link:label>
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    <link:label id="lab_ck0001710607_CounterpartyRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_CounterpartyRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Counterparty Risk Member</link:label>
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    <link:label id="lab_ck0001710607_PreferredSecuritiesRiskMember_label_en-US" xlink:label="lab_ck0001710607_PreferredSecuritiesRiskMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Securities Risk Member</link:label>
    <link:label id="lab_ck0001710607_PreferredSecuritiesRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_PreferredSecuritiesRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Preferred Securities Risk Member</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001710607_PreferredSecuritiesRiskMember" xlink:href="ck0001710607-20260914.xsd#ck0001710607_PreferredSecuritiesRiskMember"/>
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    <link:label id="lab_ck0001710607_CollateralizedObligationsRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_CollateralizedObligationsRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">CollateralizedObligationsRiskMember</link:label>
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    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ck0001710607_CollateralizedObligationsRiskMember" xlink:to="lab_ck0001710607_CollateralizedObligationsRiskMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ck0001710607_EmergingMarketRiskMember_label_en-US" xlink:label="lab_ck0001710607_EmergingMarketRiskMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Emerging Market Risk Member</link:label>
    <link:label id="lab_ck0001710607_EmergingMarketRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_EmergingMarketRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Emerging Market Risk Member</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001710607_EmergingMarketRiskMember" xlink:href="ck0001710607-20260914.xsd#ck0001710607_EmergingMarketRiskMember"/>
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    <link:label id="lab_ck0001710607_ConvertibleSecuritiesRiskMember_label_en-US" xlink:label="lab_ck0001710607_ConvertibleSecuritiesRiskMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Convertible Securities Risk Member</link:label>
    <link:label id="lab_ck0001710607_ConvertibleSecuritiesRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_ConvertibleSecuritiesRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Convertible Securities Risk Member</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001710607_ConvertibleSecuritiesRiskMember" xlink:href="ck0001710607-20260914.xsd#ck0001710607_ConvertibleSecuritiesRiskMember"/>
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    <link:label id="lab_ck0001710607_LiquidityRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_LiquidityRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Liquidity Risk Member</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001710607_LiquidityRiskMember" xlink:href="ck0001710607-20260914.xsd#ck0001710607_LiquidityRiskMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ck0001710607_LiquidityRiskMember" xlink:to="lab_ck0001710607_LiquidityRiskMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ck0001710607_BankLoanRiskMember_label_en-US" xlink:label="lab_ck0001710607_BankLoanRiskMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Bank Loan Risk Member</link:label>
    <link:label id="lab_ck0001710607_BankLoanRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_BankLoanRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Bank Loan Risk Member</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001710607_BankLoanRiskMember" xlink:href="ck0001710607-20260914.xsd#ck0001710607_BankLoanRiskMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ck0001710607_BankLoanRiskMember" xlink:to="lab_ck0001710607_BankLoanRiskMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ck0001710607_AmericanCenturyETFTrustMember_label_en-US" xlink:label="lab_ck0001710607_AmericanCenturyETFTrustMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">American Century ETF Trust</link:label>
    <link:label id="lab_ck0001710607_AmericanCenturyETFTrustMember_documentation_en-US" xlink:label="lab_ck0001710607_AmericanCenturyETFTrustMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">American Century ETF Trust</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001710607_AmericanCenturyETFTrustMember" xlink:href="ck0001710607-20260914.xsd#ck0001710607_AmericanCenturyETFTrustMember"/>
    <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_ck0001710607_AmericanCenturyETFTrustMember" xlink:to="lab_ck0001710607_AmericanCenturyETFTrustMember" xlink:type="arc" order="1"/>
    <link:label id="lab_ck0001710607_CreditRiskTransferSecuritiesRiskMember_label_en-US" xlink:label="lab_ck0001710607_CreditRiskTransferSecuritiesRiskMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Credit Risk Transfer Securities Risk Member</link:label>
    <link:label id="lab_ck0001710607_CreditRiskTransferSecuritiesRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_CreditRiskTransferSecuritiesRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Credit Risk Transfer Securities Risk Member</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001710607_CreditRiskTransferSecuritiesRiskMember" xlink:href="ck0001710607-20260914.xsd#ck0001710607_CreditRiskTransferSecuritiesRiskMember"/>
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    <link:label id="lab_ck0001710607_CashTransactionsRiskMember_label_en-US" xlink:label="lab_ck0001710607_CashTransactionsRiskMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash Transactions Risk Member</link:label>
    <link:label id="lab_ck0001710607_CashTransactionsRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_CashTransactionsRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Cash Transactions Risk Member</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001710607_CashTransactionsRiskMember" xlink:href="ck0001710607-20260914.xsd#ck0001710607_CashTransactionsRiskMember"/>
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    <link:label id="lab_ck0001710607_HighYieldRiskMember_label_en-US" xlink:label="lab_ck0001710607_HighYieldRiskMember" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">High-Yield Risk Member</link:label>
    <link:label id="lab_ck0001710607_HighYieldRiskMember_documentation_en-US" xlink:label="lab_ck0001710607_HighYieldRiskMember" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">High-Yield Risk Member</link:label>
    <link:loc xlink:type="locator" xlink:label="loc_ck0001710607_HighYieldRiskMember" xlink:href="ck0001710607-20260914.xsd#ck0001710607_HighYieldRiskMember"/>
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