I wish to make a suggestion regarding step recording in MuseScore. I'm not sure whether this is possible to implement, but I'll suggest it anyway, just in case.
The following solution is used in a competing notation program ( Musicator ) and has proved very useful:
For step recording ( inputing one note at a time without following a beat ) a "ruler" is used. The ruler is a horizontal bar hovering above the currently active staff. Inside the ruler is a set of vertical lines representing beats or partial beats. One line is a different colour to the rest, indicating the current position. By using the arrow keys left/right, you move the current position one step in the corresponding direction.
Example:
The current beat is 4/4
The ruler is set to 1/4th notes
The ruler will display 4 vertical lines, placed above the notes corresponding to each beat.
The ruler is now set to 1/16th notes and will display 16 vertical lines between which you can move with the arrow keys.
Now, with this feature activated you can play a note on a connected MIDI keyboard, and the note will be entered at the current position and value/length as set by the ruler. After you release the note, the current position will shift one step to the right. If you wish to record a longer note, just hit the right arrow key as many times as needed while still holding the key on the MIDI keyboard.
Example:
I wish to record two 1/16th notes, one 1/8th note and one 1/4th note:
I hit and release each of the first two notes in succession on the MIDI keyboard, then hit the third note and push the right arrow key once before releasing the MIDI key. I then play the last note and push the right arrow key three times before releasing the MIDI key.
This method makes it very fast and easy to record various rhytmic figures for example, as you can keep one hand on the MIDI keyboard and the other on the arrow keys and basically play the rhythm as you go, alternating between the two.
I hope this explanation is somewhat comprehensible. I can try to provide some screenshots and/or more information if necessary.
