Trying to copy/paste notes from an accordion part to a piano part--ends up pasting notes into both clefs and can't delete one without the other?

I am trying to copy the melody notes from an accordion part onto a new score to make a piano melody. However, copying the notes from just the treble clef of the accordion part, when pasted into the piano part ends up doubling so that it's pasted into both the treble clef and the bass clef. If I try to delete any note from the bass part, it then deletes it from the treble part too. So I can't just delete the doubled part (or add any notes to just one clef.)

I have no idea what to do here. If I can't just paste the notes from the accordion part, then musescore is going to be completely useless for this project and the project will take me an insane amount of time.

I can provide screenshots if needed. If anyone has any idea on how to copy just the notes from the first score, or to somehow unlink the two parts in the second score so that I can delete notes from the bass clef without deleting from the treble clef, I'd really appreciate it.