I'm new to Resolve (free version). As a programmer I kind of assumed that unconnected nodes, being unconnected, wouldn't interact with the process in any way. Apparently I was wrong.
What I'm trying to do here is find out an easy way to try out a completely different approach to grading the clip without losing the previous settings.
In the screenshot: 3 isolated nodes containing the previous grading and 1 new node for trying out alternative grading. Even though the new node has very visible adjustments, I only see the original clip in preview.
I also tried removing all the previous nodes. Only then the new node begins to work, and as soon as I add another node that is of course initially unconnected, the preview returns to the clip's default state.