Highlighting or marking collections,folders, etc

I appreciate that this is a long shot, that there's probably not a solution but I'm looking for a way to highlight or mark collections and folders in the left panel. By way of explanation, I have a plugin that creates notes in Bear and associates them with collections, folders, published folders, etc in Lightroom. This is working realy well; I can open notes associated with sources and the plugin adds backlinks in a note to a note's associated source but I'd like some way for sources to be flaggged in the UI so a user can see which of them have notes attached. I've considered colour labels but this is problematic because a) any given colour may be being used for other purposes; b) it would effectively exclude any other purpose for labels because a collection can have only one colour and c) adding colour labels can't be done programmatically.

So, any thoughts?