@jkeays My students are asking for the same thing. I think they are so used to google-docs that they somewhat expect that for everything.
I keep stressing how the peer-programming is a best practice to encourage students to do the driving/navigator piece. Otherwise, I am having students identify other ways they can split up the work. In some ways, it is helping students think about how their program can be broken down into smaller pieces an what needs to be common between programmers (variable names or IDs) and what can later be copied and pasted.
Remember that students CAN import screens, so they can combine separate design mode elements at the end by importing the screen.