It is impossible to reload file if file was changed outside IDEA and project was opened in new frame.
How to reproduce:
- open Project1
- change that File2 in Notepad, save
- open Project2 in new frame.
File2 will be marked as modified but you can't view changes even if you click Synchronize files.
Although there are 2 ways to force IDEA to reload files:
1) Close IDEA and re-open
2) Change file and save. IDEA detect external modification and suggest select valid version.
, I think it is bug.