vertical justification algorithm separates unbracketed staves of multi-staff instruments (making correct organ engraving impossible)
1) load the attached file
2) open: Format > Style... > Page
3) disable vertical justification of staves and play around with normal "staff distance" and "grand staff distance"
4) enable vertical justification of staves and play around with the staff distances and also with the distance factors above/below brackets and braces.
An "organ staff" usually uses a group of three staves. One staff for the right hand, one staff for the left hand, and one staff for the pedal. These grouped three staves should stay close together, even if the vertical distance between instruments in a system is increased by automatic vertical justification. Organ music in most cases is notated with both hands braced together, and the pedal staff is unbraced below. And in most professional engravings, the distance between the left-hand-staff and the pedal-staff is smaller (!) than the distance between the hands. This is very important for readability. The pedal should stay very close to the left hand, even a bit closer than the distance between left and right hand.
A combined staff/TAB notation (for example for guitar) uses linked staves, and these staves should also stay close together, when general staff distance is enlarged.
actual behaviour with "disabled vertical justification":
the distance between grouped and linked staves can be changed with the "grand staff distance" setting. This is more or less proper behaviour, pedal and TAB stay with the staves they are grouped or linked to. It seems that all kind of grouped/linked staves are treated as "grand staff". However, there is no possibility to change the pedal distance independent of the braced hands.
actual behaviour with "enabled vertical justification":
the pedal staff and the TAB staff are now treated as individual instruments. The automatic justification algorithm distinguish "braced" and "bracketed" staves from individual instruments, but it does not account for grouped or linked staves and it also ignores line or square brackets. This leads to an abnormal separation of the pedal from the braced hands, and also to a separation of the TAB from the guitar staff.
There is no chance to you reduce the separation of the pedal from the manualiter brace. Even "fixed staff spacers" do not work. The automatic vertical distance justification overrides the manual spacers. You will have to disable vertical justification. Correct organ engraving is impossible with enabled vertical justification.
suggestion for the automatic justification algorithms:
The "Max. grand staff distance" setting should also apply to grouped and linked staves like "pedal" or "TAB". Pedal, TAB and grouped staves in general should be treated as "grand staff", not as individual instruments. Grouped staves could either be treated as "within a brace", even if there is no brace. Or it also would be nice to have an additional distance factor for grouped staves besides brackets and braces, which could be set to 0.9 or 0.8 to tie these staves even closer together.