If I'm missing current functionality, please forgive me, but I find this ability very helpful in other systems I've used. It would be nice if there was an option for each dialog node (where current functions like "move", "duplicate", "delete" are located) to deactivate/archive it. Maybe it would then show up in a separate "Inactive Nodes" section at the bottom. Maybe it would be less work (and easier to turn back on) if it just changed color/faded/shrunk to show that it was inactive.
For instance, Zendesk uses triggers which fire sequentially, and the ability to deactivate/archive a trigger allows me to easily test a new trigger knowing that even if it does not work I a) can easily turn it off, b) won't lose my work, and c) can turn it on again easily. It also makes it easier to develop triggers well ahead of when I need them (e.g. a holiday).