I stumbled on to cookie-editor after one of the older Chrome cookie extensions decided to stop working.

I didn't see anything in the docs, so I installed it and went to the site where I wanted to edit the cookie.

I clicked the icon, and it asked if I wanted to enable permissions for "all sites" or "this site only".
I enabled it for "this site only".

I refreshed the page and re-opened cookie-editor and found it blank:

I added the cookie I wanted and hit save, and it still said there were no cookies--but refreshing the page revealed the cookie had indeed been set.

After a few more minutes, I realized it must be something related to permissions, so I went to another site, clicked cookie-editor, got the prompt for "this site" or "all sites" and this time I clicked "all sites". It started working immediately and now shows cookies on all sites.

So sort of a double-bug. I really only need to occasionally edit cookies on one site I manage--so the "this site only" permission doesn't work and it doesn't tell you that's a problem. :)

Thanks for making an updated extension! :)