Use custom drag cursor that combines "cannot drop here" icon with arrow (for systems that don't do this by default)
P2 - Medium
S5 - Suggestion
OS: Windows 10 (10.0), Arch.: x86_64, MuseScore version (64-bit): 184.108.40.20641, revision: 5b23862
Drag-and-drop of symbols from palettes onto the score is no longer working.