I just tried to double click on furniture lines and didn't have problems. Maybe your system have a very short double click delay, then you should try to double click faster.

It's not that. Double clicking those lines is supposed to always bring up the "modify' menu?
Or maybe I'm blocking it somehow...

If you want to increase the text of dimension lines (and any other text), select them and use Plan > Modify text style > Increase size menu item.

I see now. But still, i have to do this (ctrl+alt+k) each time i add a line. And it kinda defeats the purpose, since i can't read the dimension while i move the cursor.

Did you build your 11 m model with the version 3.4 Beta or with the version 3.3?

I built it offline, with version 3.3.

I fixed all the windows on my saved model, but I'll recreate the problem and send it to you.