I'm still very enjoying this (very well done) script, and would like to thank you for this.
1) Do you think it's possible to have the collection folder name(s) written into a custom field? It would be easier to know if any track is part of a collection or not. Often I forget to drag it to the Album Collection node, afterwards the fastest way I found is to check with [Find More From Same -> Album Collection] if it's already included or not in a collection. Tedious task with many involved tracks.
2) Related to first question, would it be difficult to program the ability to [Send To -> Collection folder name] tracks, similarly to [Send To -> Playlist name]? It would be incredibly easier to manage the collections this way.