API Support for Automatically Updating 'Create Tag Allowed Groups' in tags settings

Not sure, but I don’t think we have a hard limit. The UI may become quite unwieldy though.

You could maybe have a look at making a custom script with automations

If you don’t need every moderator group to be it’s own group, you could instead add that list of users to the same group and only add that one to Create tag allowed groups field. Wouldn’t that suffice?

In that case, you could take a look at An 'add to group' script for the Discourse Automation