There is a usability issue ticket out there right now to be able to globally change text without needing to select the text first.
I had an idea of leap frogging their suggestion and making it so you don't have have to open the text editor to make these type of changes.
I can't speak to how everyone uses the text editor, but for me, a large amount of time I generally do changes globally and don't fiddle a lot with individual things.
One thing we are NOT doing is on-canvas editing. I think this route is going to be the best route that has best UX.
Bug reference: https://bugs.kde.org/show_bug.cgi?id=400243