Alt click on a node connection automatically disconnect it from the other nodes. And there is some nodes which can be easily summoned by pressing a key and clicking at the same time. Like B+click will place a branch, and S+click a sequence.
If you're willing to compile it, Aseprite is a great option as well.
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GameSparks Challenges Tutorial 3 User Manager
How to manage users in GameSparks cloud-based development platform.