The rests look displaced to the left. Is this normal spacing in Dorico or is there something else going on?
That system is overfull, presumably because you’ve forced the layout in some way. If you switch on the note spacing tool you’ll see that each of the columns is the same distance apart, but visually of course it looks uneven because the eighth notes are much wider than the eighth rests. We’ve talked in the past about making it possible to specify some additional space after an up-stem flagged note, though in the case of an overfull system like this it might conversely make the music look even less even, because the space for the rests would end up even further compressed.
P.S. I understand the idea of the rests being spaced equidistantly between the noteheads, but even then they look too far to the left for my taste.
According to the note spacing tool, the systems are only 90% full, although I do have a note spacing change for the quarter note default space to be 3¼.
The rests are not spaced equidistantly between the noteheads, by the way: they are positioned hard left against the columns. The columns, however, are equidistant because they are all for the same rhythmic duration.
Yes, I can see that upon closer inspection. I understand the problems involved in allowing extra space after an upstem flag, especially in overall spacing.
Interestingly, overfilling the bars produces a slightly better result. The note spacing tool gives 113% for this system.
I need to do this because there’s no place to turn pages otherwise; it’s a chamber orchestra and the temporary loss of a player turning pages would be audible.
To my eyes that’s not really better 
I think the optimal result would be obtained by selecting the circular handle for each of those rests and applying a small graphical offset (not using the square handle, which moves the whole column) so that the rest is more visually centred between the notes to either side. Provided the staves directly above and below don’t also have eighth rests dotted around the place in the same passage, this slight discontinuity shouldn’t be noticeable to the person reading the score. Figuring out how to make Dorico do this automatically and when it would look good versus looking wrong is a bit more of a tall order I think.
If I did this in a part, would it show up in the score or do I have to propagate properties? I’m not always clear about what gets changed in a score when tweaking a part and vice versa.
Note spacing adjustments are completely independent between layouts and cannot be propagated by way of Propagate Properties, as they’re not properties at all.
Daniel, do you think eventually such offsets could be copied to other measures? In Vaughan’s 5 measure example the first measure could be adjusted then copied ahead as needed. Quite a few of us engravers do many adjustments like this to improve “optical spacing” in our work. Having this copyable would save a lot of time.
Thanks
It’s tricky to achieve at the moment because of the way the data is structured, but certainly in the fullness of time we might be able to come up with a clever way of doing this. We’ll think about it.
And it seems there isn’t even any way this is exposed to the scripting engine, at least at the moment…