As I always forget if it was startwith:abc, startSwith:abc, beginwith:abc or beginSwith:abc, I defined my own filter ^:
That way I can search for
Of course, this filter also shows up in the Filter-list (where I don't need/want it).
A possibility to define your own functions (or an extra checkbox in the filter definition: "Don't show in teh list" or an option to create aliases for existing functions or ...)
(Extremely low priority suggestion)