I use ProfitUI and the gear set button is visible and it works. I don't think Profit is doing anything that would interfere. The one thing to check is which variant of the character window you're using. I use the default window, and I haven't tested the small or large variants lately. There could be an issue there that I don't know about, especially with the small variant.
FWIW, my personal take on the gear set function is that it is no easier to use than the macros I set up years ago. The reason is that you cannot edit a gear set. Every time you get a new piece of gear, you have to delete the old set and create a new one in its place. If they ever fix that misfeature, I'd start using sets instead of my macros.
-= Therendil =-
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