Brackets between extra instruments

In these folksong collection I am writing for string quartet, at the end of the last song (on my last flow of the project), the players need to sing while playing. I added “voice” to each player in the setup menu. I have two questions- how is it possible to draw the barlines (and brackets) between voice1 and vln1, voice2 and vln2 and so on, and if it is possible to somehow have these “instruments” and staves only on my last flow rather than the entire project? I like composing on Galley view and I wouldn’t like to see all these empty voice staves until it is relevant. Thank you!

You should find that provided you have instrument changes active for the layout, those additional Voice staves are hidden throughout all the flows where the string players are also not singing. If on the other hand you don’t want to use instrument changes at all, your best bet would be to add each of the singing parts as a separate player and then include those players in each of the part layouts, so that the Violin 1 part (for example) actually has both the Violin 1 and Violin 1 Voice players assigned.

As for bracketing, you can do whatever you want with the brackets in Engrave mode. See here.