I think it would be extremely useful to be able to save search filters. For example, if I only care about one repo but my Gerrit server contains numerous ones, I can "watch" the project and get a link to see Open Watched changes. I would also like to see Merged Watched changes. I can type this in the search bar easy enough, but hey - clicking is much faster!
If this were to be implemented, it would allow much quicker access to the information that is desired without having to remember the proper search query every time.
Mergedinto: 640