When I am about to print parts I find that sometimes I have stacked things above a stave, rehearsal mark plus some comment or other. So the distance between staves gets unnecessarily big. So I drag things around creating space but when I have done that Dorico doesn’t adjust to lessen the distance but leaves a blank space. I’ve looked for some recalculate page instruction but cannot find anything. Any hints?
You can reduce the extra space Dorico calculates for text items that you intend to move around by disabling text collision avoidance for them first.
However, moving items around graphically generally doesn’t induce Dorico to recalculate horizontal or vertical spacing. (there are some exceptions, like dynamics between grand staves)
If you don’t want Dorico to consider things like rehearsal marks in the vertical spacing, you can disable collision avoidance between staves/systems for that layout. This produces totally consistently-spaced systems throughout the part, but dealing with any overlaps of notes, rehearsal marks etc between staves/systems is then up to you.