Update Issue
Latest update disabled normal controls for application. Once loaded. Musecore 4, can not minimize or enlarge screen display, can not access system information at bottom of screen, must utilize "File" control to exit application. Functions were available prior to update.
Comments
I assume you are on Windows? Yes, if you are maximized, it automatically goes full screen. Just exit that mode via the View menu or F11. This is fixed for the upcoming 4.1 release.