I need more quick launch options! 
Currently there are 8 quick launches (which is awesome btw): press up/down (2), hold up/middle/down/back (4), and combo back+up/up+down (2). There are 6 more options that could be allowed:
combo back+middle/back+down (2)
double press back/up/middle/down (4)
(combo up+middle and combo middle+down are difficult to do physically, so I would not recommend those)
Thanks!
I also was curious why the back+middle and back+down were absent, but I put one app I frequently use at the top of the app list so that a double-tap of the center button launches that one. It’s like a free quick launch option.
Those combos are hard to press. Back+up is present because those buttons oppose each other but the others twist the watch and are a bit awkward to press. Which, IMO it should be up to the user to decide not to use them but Core seemed reticent to add more things to the quick launch UI saying they wanted to keep it simpler. Same reason why they don’t let you set the combo from the watch itself and only in the Pebble app.