You can do this in the key editor.
Select both midi parts in the project window, then double click and both will open in the key editor.
The two tracks should have different colors. (Violin1-green, Violin2-yellow)
In the key editor, you’ll need to set up the “event colors” (toolbar pull down) so it colors the events by “part”
Otherwise the colors won’t help you see which track is which.
There is another button on the tool bar that you will want to use.
“Edit Active Part only” This will make it possible to edit only the active part.
There is a pull down menu next to the “Edit active part only” button.
This is where you choose which part is active.
(You can setup key commands for this…Next part, Previous part)
I do this all the time and it works great.
You can actually edit more then two tracks at once with this method.
Check out the manual because this is the somewhat quick version.