Source: mozilla/multi-account-containers#854 (comment)
- Install this extension it requires no permissions.
- Open bookmark manager Library -> Bookmarks > All Bookmarks
- Create a bookmarklet by clicking Organize -> New Bookmark,
- Name: Containerize a Bookmark
- Location:
javascript:(function(c,u){c&&(c=c.trim())&&(u=prompt('URL?',location))&&(u=u.trim())&&prompt('Contained URL to copy and bookmark:','ext+container:name='+encodeURIComponent(c)+'&url='+encodeURIComponent(u))})(prompt('Container name?','Personal'))
- Put it somewhere accessible - for example at the top of the list in Ctrl+B Bookmarks Bar - you can't launch a bookmarklet by searching for it in the address bar.
- Go to the site you want to run in a specific container.
- Click the "Containerize a Bookmark", pick the container name and copy the link.
- Create or edit some existing bookmark to set it to this link.