Ctrl+shift+P then type "key bindings user"
Re:Firefox 50.0
by spartanatreyu on Tuesday November 15, 2016 @06:52PM
(#12963426)
Cmd+Shift+P for MacOS.
Also Preferences -> Key Bindings works too but I'd encourage everyone to get used to the command palette for all sorts of commands like Set Syntax and Package Control
{ "keys": ["ctrl+tab"], "command": "next_view" }, { "keys": ["ctrl+shift+tab"], "command": "prev_view" }