Right now you can only select (and therefore filter) by Library, each of which is a separate, published file. If you have multiple primitive sets or collections within a single library, then scrolling through them to find the right variable is currently an incredibly poor user-experience. Yes you can search by variable name, but this requires you to remember variable names and it does not allow you search by collection name! This is particularly bad if you are setting up multi-brand variable architecture and surely you want to make that as easy as possible right, so people will need more than 4 modes? 

Overall, this encourages multi-file systems (so you can filter by library), which have their pros and cons, but namely that you can’t duplicate whole projects/multi-file systems and maintain the mappings/connections.