It is not uncommon to have two instruments sharing the same staff. We introduced a tool for the case when you would like to split the staff into two, so each player can have his/her staff.
You can access this tool from the voice selector.
From here you have access to some options. You can either split the staff into two other staves within the same part. Or you can create those staves into two new parts. You also have the choice to keep the original staff or to remove it.
Here is an example of the result.
You will find more information on our dedicated help page.