This is a biggy for drummers and most modern music. The existing input system is very cumbersome and very non-standard [or at least unlike any standard I have ever come across].
It should use the same conventions as virtually all the other scoring programmes, DAWs, drum charts, magazines, tutorials etc and use GM drum mapping. At the moment it is a frustrating game of hunt and pack to find out which MIDI notes are mapped to which drum.
This is particularly crucial when inputting drum parts from a MIDI keyboard or electronic drumkit.
Drum notation / scorewriting
Musescore uses a default drum map that you can customise / save / load. Each drumkit MIDI note is mapped (or unmapped) to a specific position on the staff, a voice (which also controls the stem direction) and a note head.
When writing a drum part simply place a note on the staff, there is no need to select voices or note heads!
Being able to save your own custom drum maps would be a bonus.