If what you’re looking for is something like “widow/orphan protection,” I’m not aware of anything. However, in Engrave Mode, you can “Move to Previous System” (or “Next System”). As you mentioned, you can change the spacing — and this can be localized for a line or a few measures if need be. (And as I’m sure you know, System Breaks and Frame Breaks can help neaten things up, too, if used with discretion!
As always, this should be done very late in your workflow to avoid a lot of fixes along the way.
— Jim
@benwiggy beat me to the option page! 
thank you for the answers. That option does help.
RE:
the problem with any kind of engraving option for me is that I’m "making it up as I go along " (‘composing’?)
So its now neat to show my tutor and run it past acquaintances for advice - but then re-work actual notes. Then any engraving changes I made along the line become trips and snares waiting to misformat revised music.
Even so compared with paper and pencil, or working in Finale, this is paradise 
…as opposed to Amadeus “scribbling and bibbling” (after composing it all in his head)?
Save your work file and duplicate it for a neatened up version for your tutor, or turn your signposts on to delete those “cleanups” later as you continue to add things. That way you can do the final layout work without the intermittent fixes you made along the way. (You can select frame breaks, system breaks, spacing changes, etc individually and “select more” from the jump bar to do this more quickly. BUT – save your file before doing anything destructive! 
Dorico and Finale along with the plugin Perfect Layout have different ways to accomplish the same end. Dorico tries to make the score ‘press ready’ as you compose while Finale and Perfect Layout do it after you are through composing. I don’t see one as being better than the other they are just different. There is some benefit to doing it after you are through I suppose as you have noticed when you go back and edit or change stuff. Dorico is not friendly then.
In my circle of colleges me and only one other person have converted totally to Dorico. All the others claim Dorico is too difficult to learn and/or finding stuff you are wanting to do or edit. In your case and in most cases I have found Doric has a setting that does exactly what you want. If you only know where to find it and you speak Dorico language.
There is no doubt Dorcio makes beautiful scores and parts but it could be made a whole lot easier to use.
Just a general chime in: there is nothing wrong with learning something difficult. Why not master challenges?
… and difficult is pretty often confused with unfamiliar.
