How do I combine treble and bass?

I loaded up a MIDI I made into Musescore and noticed that it's scattered the notes across 3 staves. As you can see, I originally wrote the MIDI using only 2 VST instances, with the intent of having "Piano, play_VST" to be played by the right hand and "Piano, play_VST #2" to be played by the left, however, as you can see, it's turned the right hand into two staves - one for bass and one for treble - because the right hand plays in a position that goes both above and below middle C.

Given most of the notes for the right hand are in the bass section, I'd like to move the notes that are in the treble stave into the bass stave, and for Musescore to just make leger lines for those treble notes. When I copy and paste the notes from the treble into the bass (by shift-selecting the "Piano, play_vst" treble line and hitting "copy" then shift-selecting the "Piano, play_vst" bass line and hitting paste), it instead deletes all of the notes in the bass line and REPLACES them with the treble notes....I'd like to have both the treble and bass notes in the same line though. Anyone know how to do this? I tried the steps listed on this page: https://musescore.org/en/node/12345
...but it didn't work for me. It just did the same as what I mentioned above: deleted the bass notes and replaced them with the treble. Perhaps it works differently for MIDI-converted scores?

Also, while I'm at it, anyone know how to move the "Piano play_VST" line ABOVE "Piano play_VST #2"? Obvs I want the right hand staff to be above the left hand staff but for some reason it hasn't done that be default, even though I ordered these VST instances correctly in my DAW before exporting to MIDI.