Hello,
This might be a glitch/bug. The save "quest properties" does not realize I changed "windows title" until I click the write directory.
I added pictures.
The first picture is where I change the title and Solarus does not detect the change to be saved. I normally save the game after the change and did not realize that Solarus did not detect it. It still said chapter 14....so I was like....what?
The second picture is when I click the write directory and Solarus detects that I changed the quest properties.
I have tried it now and you are right, the Solarus editor does not detect the change unless you press enter key (or something like that). If you press enter after changing the window title, then you can save the change and it works fine.
EDIT: I agree that this should be considered a bug.
Yes this is a known issue. There is the same problem in the dialogs editor.