Movementof Grand staff to adding piano accompanyment

I start my piece out with the grand staff with SATB in acapella with one verse then I want to add piano accompaniment (treble and bass staffs) below the original grand staff. My piece will basically have four staffs for the rest of the piece (voices on two and piano on two).

So the first half page or so is just the grand staff (treble and base staffs) followed by piano accompaniment and four staffs (two treble and two bass).

I have book Mastering MuseScore by Sabatella but do not fine a way to do that unless I am missing it.

Can that be done?