To help to declutter my screen, implement something that's like the 'Solo Mode' in Lightroom: an option for the left panel to have only node open, i.e., automatically close all other nodes.
To add flexibility, there could also be an option to define how many nodes are allowed to be open at the same time (options menu), but that would surely make it more than an hour's worth of job, and not sure if I'd even use it. Alternatively, you would allow a user to alt-click a node to open more than one node at a time (alt-click = example).
Bonus - this is also implemented in the tagging pane, where groups automatically collapse (optional, again).