Multi rests in orchestral parts

Can't open your pdf file. In general it's better to attache the actual score (than a pdf file/picture and so on), you've trouble with.
It's possible via right click->measure properties to break multimeasure rests, but not sure, if it answers your request.

edit: for multimeasure rests in general, see: https://musescore.org/en/handbook/measure-rests#display-multimeasure-re…

Add the rehearsal marks at the appropriate places before turning on multimeasure rests. They will automatically break the rests when you manually turn the rests on by pressing "M", or when you generate parts from a score, which enables the multimeasure rests automatically.