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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Michael Dunnam has tons of useful stuff for game developers on his Gumroad page. For example, look at these free shiny IMM brushes: 17 Accurate gemstone IMMs, all wrapped up in one convenient insert multimesh brush.
You can also check out his other IMM brushes. Here are some of the sets: