First, I’ll suggest you try out the current beta, if you can (you can download it from here: Daily Builds. You can read more about the huge number of updates being made to it by @wolthera, here: Text Tool Thread. And much thanks to wolthera, as they’ve already been making my art experience with Krita better (especially the text wrapping).
That said… Even if you use the daily build (as it currently stands) You’re still going to have an issue with what you’re attempting to do, as there still doesn’t seem to be a way to simply drag the corner of the text boxes and resize the font box (along with the text). Maybe that’s something wolthera could look at it? I’m not sure what the technical aspects of it would be. The good news is using the Daily build version scaling the font becomes exponentially easier to do. Instead of having to select the text box and then entering the editor, you can now just select the text box and scroll your middle mouse wheel over the Font Size number on the new Text Properties docker (not to be confused with the Tool Options Docker). I’ve pointed this out in the attached image. Doing so, will increase/decrease the font scale by one point, each click of the roll.
