The Grid > active nodes > Heatmap feature is great for Ram + CPU usage.
But often I would just like to figure out, which nodes are "really" doing something.
I measure this by having a look at the running builds of a node.
Builds can have such a small memory footprint or CPU usage, that I don't see in the Ram/CPU heatmap.

Adding a 3rd option to the Heatmap dropdown: "Number of running builds" I could easily check, which VMs are idle at a specific time frame.