Just like in this, closed, post, I too, would like to be able to disable or, better yet, remove the “custom” tab, where I don’t want it.
I have a few dropdown like in that post, including ones that fetches all useable options by API.
I fail to see why we must have the “custom” tab forced in, when we’re providing an exact list of possible values these fields can hold. Offering the user an option to put just about anything in is the exact opposite of what is wanted in these cases and just means needless validation work, begging for errors to occur.
Surely it wouldn’t be the hardest task, to at least allow the “custom” tab to be disabled/locked, if you’re hell-bent on having it present everywhere.