This piece will be following a “non-traditional” approach. Is there any chance I can achieve this in dorico? If not, I think I’ll probably be dealing with it in something like illustrator, but figured I’d check first.
Main things: adding the new time signature to the new measure.
Having the barline end where I drew it in only for this new measure.
I can’t help with the bar line but I think the time signature could be solved by Dan’s MusGlyph font and just entering it as text/system text? I actually did this the other day when I needed a third large time signature at the beginning.
The last note in the extra staff is inside a 3:1e tuplet, and the eighth rest that follows has been made transparent.
Edit: When the independent time signature is added, the barline join between the main staff and the extra staff is lost. It can be replaced by a vertical line with a thickness of 1/5 space.