Implode when one stave has 8va----- and the other doesn't
- Create a score with two staves.
- Add notes to a bar in each stave.
- In top stave, mark whole bar 8va alta
- Select both staves
- Choose Tools | Implode
The resulting stave is confused, with one voice requiring the 8va and the other not.
I think it would be best (in the case where two staves have different 8va/15va settings) to choose whether the combined parts should or should not use 8va, then write the parts up/down an octave as necessary to represent the same pitch.