Hi all,
Found something by chance, I’ll just post it here in case someone else finds it useful.
Let’s say I just finished a layout for Horn 1. Ten flows, so some layout work has been done, some note spacing changes and some staff spacing changes. I have even adjusted the frames on some of the pages.
Now duplicate part. Rename to Horn 2. Check Horn 2, uncheck Horn 1. Now you have two identical parts, all tweaks have been transferred to the new part.
This method goes a bit further than the standard routine of propagating layout options and system breaks.