I'm trying to just add a single character 复, and when prompted to select which traditional variant I want I chose 覆 , but it makes no difference because one of the other variants automatically replaces it.

The reason I'm doing this is because when I go to the character 复　, and then click on it's magnifying glass, and from there click on on 覆, it shows that this character hasn't been studied, even though I think I have studied it on Skritter.

We changed the way that the simp-trad mapping works for 覆 a while back, so this bug is probably a remnant of that. We had 覆 mapped as a traditional of 复 but then changed it to its own simplified character, or maybe it's the other way around--I can't remember, but Chris will know what we did. It's not a perfect solution either way. I probably just need to delete one of the old vocabulary entries or the other.

Okay I've removed that erroneous vocab. Try adding 覆 straight to your studies and it should work fine.

Thanks for the report!