This is more like a (missing) useful feature, than a bug: when working in a file and opening a new file, FET should warn about saving the current working file. As of 5.14.5, it does not warn, so changes may be lost in the current file.
OK, by popular request: recent files list and if you change the file, FET will show that and remember that the file has changed. Please get snapshot and let me know. Horatiu, since you proposed this, I expect you to help me testing this, as much as possible.
Minor potential problems:
1) When you modify a constraint and press "OK", even if nothing has changed, FET will consider this a change.
2) The File shortcuts tab, has a weird aspect. Do you accept it as it is?
Horatiu, I added a new snapshot, minor improvement to avoid flickering of the main bar modified file flag when opening a file. Please get the new snapshot.
will do, but later this evening