Rated 5 out of 5 stars

The new version seems to require complete removing of the older one (update from the menu is not enough), and next fresh installation. Then the Emoji button shows up in the tool bar, and the extension works.

This review is for a previous version of the add-on (1.102.9). 

Rated 2 out of 5 stars

After update, this extension doesn't work anymore... A small panel with emojis does appear on the left (instead of right as in previous versions), but selecting any of them has no effect. No way to copy emojis from there either. Too bad!
(Thunderbird version 102.2.2)

This review is for a previous version of the add-on (1.102.9). 

You might need to make sure the cursor is in the body pane right before clicking the emoji button in the toolbar.