If I save the permanent defaults on a light LOP node with Redshift installed, the non-redshift settings get saved fine, but nothing under the Redshift tab gets saved (and shows up the next time I create an instance of that node). Is that a bug or a limitation?

Thanks

The delegate-specific render settings on the rendersettings node are not part of the node definition, so won't be saved as part of permanent defaults.

The settings tab for each render delegate is added on node creation. Changing the defaults would require modifying the dialog script file distributed with the renderer. Perhaps placing another DS file somewhere higher in the path would take precedence, but that's not something I've tried.

The closest thing to saving defaults for a node with custom spare parameters would be to create a shelf tool that creates the node. Drag any node to a shelf to add the node. Then it can be recreated as is by clicking that shelf tool or using it from the tab menu, (may require editing the tool to add it to the proper context.)