Is there a fixed ratio for converting the space designations used in ideal vertical distances to the inch/mm designations used the vertical spacing of engrave mode?
Related issue: If the space designations in the ideal vertical spaces are changed, how does one update the project document to reflect those changes?
I don’t understand this question. Perhaps the manual will help?
Per-layout vertical spacing options • Dorico Pro Help • Reader • Steinberg
The changes are done automatically, unless you have already prevented them by making manual changes (I think).
The height of a space (the distance between two lines on a staff) is defined for each layout in Layout Options > Page Setup > Space Size. Any measurement given in spaces, like the ideal gaps, is therefore a relative measurement, not an absolute one – the absolute measurement depends on your defined space size.
So there is not one unchanging “fixed ratio”, but you can do the math yourself by multiplying any measurement in spaces by the defined space size for that layout.
I’m not sure what you mean by “update the project document”. Any changes to those settings take effect immediately (unless you have already made manual changes, as @janus says) and will be saved with the project.
Thanks for the responses. My concerns have been put to rest. I’m deep into the process of moving from Finale to Dorico and every little bit of info helps.
You might also find this comment and this one useful on the topic of measurements in Dorico vs. Finale.