control-F and look for the group-name, this will get you nodes in the editor at least you can narrow it down
else make a material instance and you can at least see what is where
if you control-click to select multiple items, you can at least change the group-name at the same time for all of them
also, all the nodes you see in the coding UI are xml-based, parsed into whatever by the UI in the editor. select whatever, copy, paste into notepad++ (or whatever) and then look for the group-name. control-f/control-h and replace the group-name, copy/paste back into the editor.