Often when I get a match on gedmatch or 23andme, they have very little paper genealogy to go by. Sometimes, I can find their surname or one of the few surnames they have researched amoung my many wikitree cousins. However, doing so right now is a bit by random chance.
I really like the familylist and it's been very helpful, but it would also be useful to go "horizontal" as well and have an easy way to search cousin surnames, up to a limit of course.