Not sure if this is helpful for you:
You can allow empty staves to be hidden in all systems in Layout Options.
And bar numbers shouldn’t be a problem at all because you can insert a Bar Number Change anywhere.
Thanks, Florian. The problem with Hiding staves is that it is global to the document. I’d like to hide staves in one Flow, to exclude them from that section altogether; but in flows where those instruments play, I don’t want the staff list to be constantly changing, just because an instrument has rests for a whole system.
Yes indeed.
Let’s look at it this way: the fact that Dorico is severly lacking flexibility in the area of staff management now might be indicating that great things are to come. I’m looking forward to another jump from ‘not possible’ to ‘the best implementation currently available’. 
Sounds good to me!
David
Here’s another situation where a new flow seems to be forced on me: If I want “double bar, system break, forward repeat”, I have to have a new flow. (As far as I can tell.)
(Or indeed, any other style of barline but the default before a repeat on the next system.)
There’s an option for that: Engraving options (cmd+shift+E / ctrl+shift+E) > Barlines > Barline at the end of system coinciding with start repeat
So many options! Thanks.
Was going crazy when I could not enter a “forward repeat” bar line. Glad I found this and was able to adjust the system break. Hope it will be possible to enter a forward repeat without regard to system breaks in the not too distant future…
Hi,
New user here. I have been running into the same problem as Ben. I am trying to learn the program properly, so with as much automation as possible.
I would like my bar numbers to continue over the flows. To continue the bar numberings, I could change the number in each flow to correspond with the last bar of the previous flow and adding 1, but I can not imagine that this is the easiest way. Am I missing something?
I’m afraid it’s still the easiest way. You can of course get the number of the final bar by selecting something in it and looking at the status bar underneath; and then select and right click on the first bar of the next flow.
Ah I see, but then you would still have to manually type in the new bar number right?
Yes.