I don't know if a similar suggestion has already been made.
I have folders of shots that either are waiting to be processed, are currently being processed or are already processed. In my workflow I usually dump new pics in dedicated, 'to do' folders where I first rename them, then I start processing them, and eventually I dispatch them in their destination folders.
If I need to review and/or reprocess pics in a given folder I usually move it in a 'to do' folder but it's a little cumbersome and you can't move folders in DxO OpticsPro.
Yet I would find it handy if I could tag the folders with color dots like in the Mac Finder. The nice thing would be to use the latter and/or the equivalent in Windows so one could use the same code on all the environments.