[nicolas-p]

Ideally, Skov would need an integrated version control system that understands the visual code.

But now, all you can do is export your code to text files (Ctrl+S) and use traditional text-based diff/merge/version control tools.

[DonaldFisk]

This is the right answer, at least for visual dataflow. It should be done by diff/merge of graphs, displayed visually, not by converting it into a text-based format and using something like git, Perforce, or cvs. Dataflow can be expressed textually, but you'd have a hard time following the code.