You may notice that some Text Shortcuts (Quick Text) you've created are missing from the list in the Salesforce Gmail/Outlook Integration panel, or you see the error "That Shortcode is Already Taken" when creating a new one.
Cause: Quick Text is not enabled in Salesforce Classic (even if it's enabled in Lightning), or the Shortcode you're trying to use is already assigned to another Quick Text record.
Quick Text must be enabled in Salesforce Classic as well, even if already enabled in Lightning Experience.
Note: Once enabled in Salesforce Classic, Quick Text can't be disabled. It's automatically enabled in Classic orgs where Chat is enabled.
Using Developer Console:
Using Workbench (a free, community-supported tool, not officially maintained by Salesforce):
Quick Text Considerations: https://help.salesforce.com/s/articleView?id=service.quick_text_considerations.htm&type=5
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