Rehearsal marks have been my nemesis with Dorico. When using the defaults (at least defaults that I have inherited of numerous Dorico releases,) adding a rehearsal mark often takes a neatly formatted part and does unspeakable things to it. I found I was spending more time monkeying with final layout issues related to rehearsal marks than all other issues combined. I had reached the point that I was about to abandon the use of Dorico rehearsal marks altogether and try to cobble together a decent workaround using system text.
But before I did that, I decided to have a go at tweaking the attributes/rules related to rehearsal marks. I’m happy to report that I found a combination of parameters that mostly lay out automatically with pretty good results. It isn’t beautiful, but very functional, with a minimum of ENGRAVE mode tweaking required.
Here are the parameters I ended up with (the ones in the rightmost column):
Surprising to me, small changes made a huge difference. The basic problem with rehearsal mark layout is that they take up vertical space. That forces systems to be way too far separated in many cases. That leads to a general over-commitment of vertical space on the page (e.g. 105%). And when that happens, it is a real mess.
The first thing I did was to switch from using circle enclosures to rounded rectangles. That saves space above and below, and the layouts were immediately better behaved. The other big change was to tell Dorico to put the rehearsal mark all the way at the left of the page if it comes at the first measure of a system. I often lay out my parts so that musical sections begin on a new system, so this is a very useful option for me. There is generally ample white space available above the clef without any collision adjustments needed.
The other changes were mostly minor to try to give it the best appearance.
So if you have found rehearsal marks to be a pain, I encourage you to try some of these options.