Hi Justin,
Could you set it to a default value and then let the Automation overwrite it? Though to be fair if it is a key field and you are using it in relationships now that you aren't able to rebuild then that would be less than helpful unfortunately. There isn't a function to pull just the UID from a user via a formula, just name or email address and as such if either changes Quick Base won't be able to update without going back to update from the source as it changes. If being able to pull the UID is something that would be helpful you can submit that as a User Voice feedback even if that wouldn't help you with your use case today. Sorry there isn't a formula function or trick I can suggest in this instance.
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Evan Martinez
Community Marketing Manager
Quick Base
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