How to Make 1 system name for 2 staffs with subnames?

Speaking as a vocal music educator, I have no authoritative knowledge of instrumental score conventions. Seems to me, larger scores have individual staves for one instrument within the instrument family. Such as, a stave for french horn 1, another stave for french horn 2, and so-on. I'd SUSPECT there are professional notation editors who designate ONE stave for french horn, then where a 1rst, 2nd, 3rd part happens, at that measure some indication is made of the multiple players assignments. From the CHORAL perspective, when multiple alto parts happen, a 'div.' (division) notation suffices, and the women singing alto understand part of that group will take whatever notes the conductor chooses.

You do understand that what may be "not easy for you to read" is an individual perspective. I'll be interested if somebody with current strength in MS4 will chime in to advise how you might get the look-and-feel you want.

It's not exactly as shown on your example, but I don't know how to get it more similar. At least this solution will repeat reliably with short instrument names on each subsequent system.