Not sure how this happened, but in my first foray into master pages I created new Score and Part master pages and saved them as a set. Only problem is all the parts (a big orchestra) are set to use the Score master page. Is there any way to change them all to the Part master page in one go?
Open Layout Options, use the Select All Part Layouts button in the bottom right corner, then set the Master Page (in the Page Setup section IIRC) to use the relevant Master Page Set. Apply and Close.
Leo, I owe you a pint. Or 10 
Related question: I keep deleting the Default master sets so I don’t accidentally use them in this project, but the pesky things keep coming back on reloading the project. Any way to prevent that? Not a biggie but I like to keep things tidy.
It’s not something I’ve ever experienced, but I can’t say I’ve ever tried deleting them. Would it make more sense to adapt them and use them, rather than starting again from scratch? Unlike most other Dorico defaults, default master page sets are only default for the project in question.
I would modify (change) the default master pages to look like what you want. Why reinvent the wheel? I don’t know why they come back after being deleted, but it’s apparent that’s expected behavior.
Leo - That’s a thought, however in that case I’d also like to rename them to make it clear to myself that I edited it for a purpose - however it silently prevents you from renaming the default sets. So could be a little confusing then if you edit the master pages for the default set, well because then it’s no longer default is it? Sounds like nitpicking but in game development we have at least 10 different workflows we switch between (audio, art, programming production, …) with thousands of assets being created across the team, so having things clear and obvious is important.
And besides, I want a single consistent house master set, so the defaults become irrelevant except for setting up projects and one offs.
Yeah looks like Dorico wants to have default sets in there no matter what, except it will let you take a hatchet to them in project (while still calling them default sets). Seems like this could be made a bit cleaner but I won’t sweat it.
I would modify (change) the default master pages to look like what you want. Why reinvent the wheel?
Because of what I said above - we’re constructing a house style to be reused in many assets (pieces), so when creating a new piece first order is to load up the custom master set and use it across the board. Only (small) issue is I can’t get rid of the default sets in there, which would be good for clarity and so neither I nor assistants accidentally mess it up.
Just for interests sake - the house style must include information such as asset tags and timings, so that as this flows through the process from scoring to stemming the tags identify the asset and intended location in the game. Dorico is really a productivity boost for this and for many reasons!
Apologies, I forgot that you asked this in another thread. It’s expected behaviour that the 2 default sets get regenerated if they were deleted. (And you can never delete the last master page set in a project.) I’ve made a note to add this info to the manual.
Other users may guide you otherwise, but as a “house style” would entail a combination of Engraving/Notation/Layout options, paragraph/character/font styles etc in addition to master pages, if you want a reliable template you might be better off currently by setting up a read-only project with everything set-up as desired, and build new projects from that base.
Re: default sets - no problem.
Great tips on the house style, will do.