Musescore 3.0 Mixer window cannot be resized by default
The Mixer window cannot be resized if the menus displaying the Name, Patch, MIDI etc. are shown. If this menu is hidden by the arrow below it, then the window can be resized. If the menus are shown and the window is resized by dragging the bounds upwards, then the Mixer window will drop (to system tray?) and cannot be accessed until the client is restarted.
OS: Windows 10 (10.0), Arch.: x86_64, MuseScore version (64-bit): 188.8.131.5285, revision: c1a5e4c
Screen resolution: 1920x1080