Vivaldi

There is no easy way.
You can set every staff to piano in the staff/part properties menue.
You may change the alto clef to a treble or bass clef.
You should rearrange the staffs so that all treble clefs and bass clefs below each other.
Then select all treble staffs and use Tools/Implode. Do the same with the bass staffs. Now the second treble line will be copied to the first one as voice 2 (and 3 and 4 if necessary).
Do the same with the bass staff lines.
Add an extra piano and copy the first treble staff to it. Do the same with the first bass staff.
Now you may delete (of hide) the original lines in the instrument dialoge.

Finally, you need to edit the direction of the note stems, delete some double notes, and much more. You have to go through the score measure by measure.
To make it a little easier, use the selection filter and sometimes it's wise to swap voices.

I believe, it is a lot of work :-).

By the way: there are several measures with a wrong lenghth. So see measure 12 and many after measure 136. Probably wrong time signature.