I've just discovered one of our tables has duplicate entries which you would think isn't possible but it turns out you can have an inactive "Herts" and an active "Herts" and RE doesn't realise you have the same thing in the table twice.

Only way to remove one is to rename it, make both active (you can't make the inactive one active until they have different names) and then merge the two table entries. It's deeply weird that you can add the same thing to a table twice.

The perception that you need this may be based on the way you are using Attributes and Tables. Limit the options in both, and avoid one-offs of either Attributes or Tables that will just be used once. Harder to pull by range, harder to remember how it was used, harder to report/query. So if you have an attribute of 'Board Member', its table would be 'Years', 'Gala Attendance' would also link to Years table. Multiple attributes using the same table, so there will be a lot of duplicates of the table entries to different attributes, and fewer of them as an option, if they are created and used correctly. One-offs then will be in the rare, specific Attributes, and can be restricted to one entry.