Add "Above/Below System" to measure number's "Placement" property
In a score with multiple staves:
1) Add measure numbers to score in Style menu.
2) Change Vertical placement to Below.
Expected behavior: Measure numbers appear below the entire score, regardless of how many staves there are.
Actual behavior: Measure numbers appear below the topmost staff only.
Workaround: Set measure numbers to all staves. Make all measure numbers invisible except the bottom staff.
OS: Windows 10 (10.0), Arch.: x86_64, MuseScore version (64-bit): 184.108.40.20699, revision: 43c5553