If you select a note in the matrix editor and hold the
mouse button down, you can drag the note to a new pitch
or a new start time or both. This is very useful.
However, it should be possible to drag a note to a new
pitch such that the dragging movement is constrained to
be vertical, thus avoiding the risk of accidentally
changing the start time of the note by accidentally
moving left or right from the original position of the
note. With the present unconstrained method of
dragging, it is all too easy to make an unintentional
small horizontal movement especially when positional
quantisation and the grid are both disabled.