Kate is the editor i'm using these days on Linux (even though i use Window Maker for my WM and not Plasma) but it does have a few weird aspects. One of them, which annoys me, is that every "tab" is really its own entire editor with its own state - if you do something like search for a word in one file then switch to another tab, you can't use F3 to search for the same word again in that file because that's actually a different editor and it doesn't know that you searched for something in the other tab. This extends to other stuff, as if the main Kate window is just a window manager for the editors it launches in it and it just pretends the UI is shared.