You should be able to drag from one staff of the piano to the other by moving a little way horizontally so that Dorico knows you want to do a rhythmic drag rather than a pitch drag, then move to the other staff.
Congratulations on Dorico 5! Another big step forward! I am very happy with the new version!
Mouse editing is my favorite new feature in Dorico 5! The lack of this feature was one of the last reasons why I still often do compositional sketches with Logic.
But I hope that the function will be further developed. Important for me is:
Chromatic dragging (perhaps with a modifier key): i.e. shifting to all other 11 pitches and keeping the original intervals
Diatonic dragging with acceptance of chromatic steps
Examples:
Now (in c major) e, f, f#, g dragged to f results in f, g, g, a.
chromatic dragging would result in f, g flat, g, a flat
Diatonic dragging with acceptance of chromatic steps would result in f, g, g#, a
Further wishes:
Horizontal and vertical dragging at the same time (simple and easy to control in Logic!)
At low zoom it is difficult to see how far you have moved the notes vertically or horizontally. A small pop-up window indicating the interval or note value that has been moved would be very helpful.