Add div in strings

You can add either a staff to the violin or an entire new violin, I suggest the entire new violin because adding the part has certain limitation that might cause you problems in this score. Enter all of the notes in both staves without worrying about the extra staff everywhere. After all of the notes are entered on the staff you sometimes see, right click the staff, choose staff properties and set the "Hide when empty" option to "Always" and you will only see the staff on systems with notes. To make the empty measures also invisible as in your example, check the Cutatway option above the Advanced Style Properties button.