I mean you can't alt+f for file menu or alt+e for edit, alt+v for view etc. Maybe I don't know something... I want something like alt+f3 for windows' actions but for menu (alt+f would be just great). I've searched for shortcut for this but found nothing.
When you chose title bar button for menubar style of course.
Indeed - there is ability to set keyboard shortcut for global menu panel widget - but there is not ability to set keyboard shortcut for revealing global titlebar menu
You can press ALt+F for "File" menu if the application exports that (Qt apps do since 5.7.1 or so) but I agree there should be an assignable shortcut similar to Alt+F3
*** This bug has been marked as a duplicate of bug 379242 ***