3.5 Beta: Time Signatures Text
I noticed that when I want to apply a new text to a time signature, in a score with more than just 1 instruments, it will apply the new text only in the instrument's time signature I selected...
Also do you know how I can write this more elegantly: 
Comments
As for the final part of your query, it was the subject of a thread I started a couple weeks ago, complete with a load of replies questioning why one might want to use multiple time signatures in the first place! ( https://musescore.org/en/node/305902 ). When I write "6/8(2/4)" or the like, I create the second part by icons from the symbols palette (make sure you match your font!), which allows you to write parentheses which span both digits. BUT it's a pain in the ass (hence my thread.)
As for the first part, working with 3.4 yesterday, I had the same problem--some of the time. Other times, when using a CTRL-C copy, for instance, or adding another part, it seemed to work just fine. Go figure.
In reply to As for the final part of… by wfazekas1
I see... Thanks for notifying me.
Yes, time signature properties apply to just that time signature. If you want to then apply that modified time signature to multiple staves, best to create a new time signature set up that way then add that to your score.
In reply to Yes, time signature… by Marc Sabatella
Oh that exists too... Although kind of weird.