I would suggest to change a little bit behaviour of Open/New/Save to be as common as with other software working on documents.
- If you exit program with unmodified file then no warning;
- If you save file manually then clear modified flag;
- If you press New and current file is modified then warning and possibly save
- If you press New and current file is unmodified then no warning
If I'm right the only issued warning is when you exit program regardless whether file is modified or not.
There is also warning/confirmation if you want a new file.
I'll think of your suggestion and add it in the TODO.