Addon works via right-click, however toolbar icon refuses to pin.

[mwoffenden]

Installed on Firefox 123.0 (64-bit) on M2 Macbook Pro.

Addon works via right-click, however toolbar icon refuses to pin.

It does have the "Access browser tabs" permission.

[Zegnat]

This add-on does not register a toolbar icon at all. So it is correct that it does not pin. When are you given the choice to pin it?

Note that Firefox has made the decision to show all add-ons when you click the built-in Extensions button, even those who do not have a button that can be interacted with. There is nothing to pin, it is just Firefox showing you an inactive logo and name.