Could you be more specific?

From what I understand, you seem to be missing the add-on icon in the firefox toolbar strip.

But that feature hasn't been removed. So the icon should still be there.

It may have been hidden automatically if the toolbar strip got too crowded.

In that case, look for an icon that looks like a jigsaw puzzle tile. Click on it to see the hidden extension icons.

If this is not the case, could you open an issue at the support site (https://github.com/jyshb/pin-unpin-tab/issues) with more details, or could you email me? You can find the contact email on the extension page as 'Support Email' or something similar.