Kenneth’s almost definitely right.
However, resetting cross-staff notation to put notes back on their original staves only does half the job - it’ll just give you all the piano chords on ONE stave.
My advice is:
- Do what Kenneth says. Make a note of which stave the notes all jump to. I’m going to assume treble in the following instructions.
- Ctrl/Cmd-Z to undo what Kenneth’s suggested.
- Select everything on the bass staff (either by drawing a marquee selection or by clicking the first note, holding Shift and then clicking the last note)
- Type N. You should see everything from the bass stave jump to the treble stave but remain selected.
- Ctrl/Cmd-X to cut.
- Put the caret in place to start note entry in the bass staff.
- Ctrl/Cmd-V to paste.
If I was wrong about all the notes originating in the treble stave then swap my basses for trebles and my trebles for basses.
This took 5 minutes to write, but takes about 5 seconds to do. Good luck!