@ehitonandakedone
Not sure what you mean with “at the same height as the beam of the adjacent quintuplet”.
But you can move individual rests position from the Properties Panel (select the rest first…):
You can also set the desired position of the beam itself, in Engrave mode (select the Beam and use the move shortcuts (*):
(*)
Excerpt:
Can you describe what you need more precisely, and attach a Dorico file example?
Also may I suggest that you edit the title of this thread (clicking on the pencil icon near it), and write something like: “Stemlet beams [or beams over rests] and notehead size”? That would be helpful for other users searching the Forum.