simply doesn't show up anywhere

Works as of 80.0a1. Unfortunately it doesn't show up in the browser toolbox but does show up in the browser content toolbox. And unfortunately for me it doesn't show local extension storage, so anything committed by an extension with storage.local won't show up under local storage. I think anything committed with storage.sync will show up under session storage though? But yeah unfortunately that means you can't use it to find stuff like extension settings, unless they are stored in the local storage for a non-extension URL, or stored in storage.sync. But a recent update to firefox put a storage limit on storage.sync, now you can only have a total of 100KB of synced storage per-extension. Which is barely enough for settings, not enough for extensions that might store custom user scripts or rules, stuff like greasemonkey or ublock. So most extensions are using storage.local now or will be converting soon and that means their storage can only be accessed in about:debugging.

To the person complaining it's not in the toolbar — that's not how this works. It's not supposed to show up in your toolbar. It's supposed to show up in your browser content toolbox, hit ctrl + shift + i.

edit: cool thanks for the link. hopefully you can find a way to add extension storage, it seems like the only way i can view local extension storage nowadays (the contents when an extension calls storage.local) is to go to about:debugging, inspect the extension, then use the native debugging toolbox Storage tab. but it's sort of flawed formatting and so inconvenient to get there from about:debugging so i always wanted an extension to integrate it in the main browser toolbox

I got this extension for firefox on windows 10 and it doesn't even show up on the toolbar. Useless.

Seems to work with Waterfox Classic 2019.12, which falls slightly below the requirement for Firefox 57.0:

https://s.put.re/AugS8trM.png