Staff division on part of the score

Hello,

I am copying in musescore 4.4.4 a printed choir part to have playback options to work, and I have a problem :
In the original part, there are eight staves (SSAATTBB), but divided staves merge at one point and then divide again. For example, both sopranos have very different parts at one point, so they need to be on separate staves, but further down they merge into one soprano part.
I have found staff divide arrows in the master palette, in the Symbols section, but they locate at the wrong place and anyway don't seem to actually merge two staves after them.
Is there a way to merge staves and then divide them again ? It is something quite often seen, at least in choral music. I've searched with the search engine but cannot find a way to do this.

Thanks in advance for your help !