Well, I will probably never fix this one, but I will leave this here in order to remember.

Long time ago, KSP 1.8.0 broke the UI_ScaleEdit, UI_FloatEdit and UI_FloatRange (that I'm aware) due something missing on the prefab.

Now and then some user asks for it (as this one) - why they would want to run 1.8.0 is beyound me, as it was terribly buggy and I'm not aware of anything that works on 1.8.0 that it's not working on 1.8.1.

But yet, it would be "nice" to have Recall fixing this one just for the sake of completude.