Doesn't work with 67.0.1 (64-bit) version.
While opening "Manage All Cookies" the list of domains is empty.
Answer from the author:
Go to the add-ons page, click on the "Cookie Quick Manager" add-on to get to the details page for the add-on, scroll down to the part that says "Run in Private Windows" and select the "Allow" option.
Until I did this the "All" context would not show anything and some of the other contexts would also be missing cookies. I assume this is because when it tried to enumerate all the cookies, it would hit the "private" cookies and was denied access and instead of just continuing it would halt/crash the add-on.