Cookie editing is still missing. Without this feature a wider adoption of FF dev tools or its full utility as a wedev tool is impossible.
Yes, I voted for https://bugzilla.mozilla.org/show_bug.cgi?id=1031192. Please do the same. Thanks.
Here is the entire documentation: https://developer.mozilla.org/en-US/docs/Tools/GCLI#Commands (links to list of commands, I suggest reading the entire page).
The best part is that it is extensible (Scratchpad FTW!) :)