Chapman Stick tablature variation and questions

Hi all

There's an excellent guide to creating a chapman stick tablature score here: https://musescore.org/en/node/321170 but the Stick tab used in the guide above uses a guitar and bass pair of linked staves to lay out the music. You therefore have 4 actual staves onscreen -- treble (T) with linked tab (TT) and bass (B) with linked tab (BT). These are two instruments. That means you can have, top to bottom, any of:
T TT B BT or TT T B BT or B BT TT T or T TT BT B (what I use) but NOT T B TT BT or any other combination that places T and B together without splitting TT and BT. Is there a way to do this because I can't find it.

While trying to find it I have gotten puzzled by the Instrument panel in that I cannnot, for instance, change an nlinked staff tab to be linked without removing the unlinked one or change the clef of a staff (eg guitar from treble to bass) once I've added the instrument. Also I can't remove all instruments from the score during setup if I want to remove a guitar staff and add a bass one instead. All very trivial but counter-intuitive.

I would post a picture of what I want but, as I only have MuseScore and it can't do what I want I'llleave you to imagine it.

Finally, there is a semi-tab system used by a few Stick Players where the different fingers used to play the notes have different shaped noteheads -- circle, square, triangle and diamond. While these are all in the SMUFL glyphh list they are not all in the notehead families in MuseScore. Is there a way to add noteheads to families or create custom notehead families because, again, I can't find it.

Cheers

AxS