Mmh, can't seem to add this to my Collections, since I want to have my Subscriptions in some logical categories of mine. The same problem arose for this: https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2622976974
Because, I think both yours and this Mod can't be found in the Workshop through the Search Bar, so it may be because it's Private/Unlisted by Steam? At least I wanted to share this little inconvenience of mine.