I've never posted a review before for a Firefox add-on, but this one is so elegantly implemented (and so sorely needed) that I felt compelled to do so.

This add-on is a simple solution to a vexing problem of how to force a bookmark to open in a specified container every time. Kudos to the developer!

If it's not entirely clear from the add-on description, once you've installed this add-on, you can replace any Firefox bookmark with the ext+container command syntax and that bookmark will always open in the specified container automatically. For example, if you have a bookmark to www.google.com that you want always to open in your Google container, first make sure you've created a container named Google, then right-click on your bookmark, select Properties, and change the location from https://www.google.com/ to ext+container:name=Google&url=https://www.google.com/

One note to other users: If your container's name has any spaces or other special characters in it, you have to urlencode the special character in the command (like replacing spaces with %20). For example, if you want your bookmark for www.bigbank.com to open in your My Banks container, the bookmark would be ext+container:name=My%20Banks&url=https://www.bigbank.com/

I would rate it 10 over 5. The add-on says what it does and does what it says. It may seem obvious but I'd like to suggest the developer to highlight that if a bookmark adheres to the "ext+container:name=MyContainer&url=" syntax it will open in "MyContainer" directly. That's a very good thing to have

Does what it says and does it right.
I love this.

Works well with bookmarks! Thanks!

I have been waiting for something like this for a long time. I can finally set up my password manager to open different accounts on the same site in different containers.

Edit 09 May 2020
Here is an example you can share. I use KeePass 2 password manager, which allows an override URL for specific entries. I have two Amazon accounts, which I open in different containers. In the Override URL field of both, I put
cmd://{FIREFOX} ext+container:name={GROUP}&url="{URL}"

The entry I put in KeePass' Work folder automatically expands to
"C:\Program Files\Mozilla Firefox\firefox.exe" ext+container:name=Work&url=https://smile.amazon.com/

The entry I put in KeePass' Personal folder expands to
"C:\Program Files\Mozilla Firefox\firefox.exe" ext+container:name=Personal&url=https://smile.amazon.com/

Exceptionally useful.