I suspect this isn’t possible, but… is there a way of having ossia staves show/not show on a case-by-case basis?
I have a few instances of ossia staves I don’t want showing in my full score, but one specific instance where I DO want the ossia to show.
I tried making an additional staff, which would have worked except it won’t let me resize it to ossia-size without also affecting the staff it’s attached to.