I do not seem to be able to find a clear answer to this, here or in the Dorico help.
I use the “Add bar number change” to insert any bar number I want anywhere. But I do not find the way to decide the individual aspect I want for any of those numbers: the use or not of an enclosure, or the font for any particular number.
Tried if using rehearsal marks using bar numbers as index could be changed, but didn’t dind a way too. Just the color again, which now includes the border