"Prevaricating cross-staff" needed.

There is a real need for what would appear to be cross-staff between score-adjacent, but different, instruments. Right now, cross-staff is limited to adjacent staves of a grand staff. Here is an example: https://musescore.com/user/1685616/scores/5394313 . The score (the relevant measures, at least), are as they appear in the esteemed Peters edition of "the Organ Works". Appropriate style considerations mandate that this be played on two manuals (keyboards). If simulated on MuseScore, with two instruments, or MuseScore output used for driving a virtual or actual pipe organ system, the upper staff must be one instrument-channel and the lower another. If set up this way, the cross-staff notation in mm. 3-4 would not be possible for want of this feature. This sometimes occurs in Bach organ scores. (This score's audio was produced by a second, non-posted copy of the score with discrete instrument-channels and (consequently) no cross-staff notes). It is fair to say that MuseScore cannot simultaneously represent and correctly render this brief composition correctly.

Another way to deal with this, a groß kludge, would be inspector control of channel on a per-note basis. Hidden staves are no answer, either (and don't yet work correctly in MS3). But we do have a problem here. Gladly Bear wants a cross-staff (cf. BWV 56).