I think you're referring to the Emoji addon. You may have the addon and it might be disabled.

I have Awesome Emoji picker enabled. The emojis appeared on the right side of the compose email page. The appearance was like a split screen. Type email message on the left left side and could select an emoji from the right side of the page. I am running version 102.2.0 so I am not sure if an update made changes in the appearance of the email page but something happened and the emojis disappeared. Is there another solution to restore the emojis?

Addons sometimes work differently with upgrades. You might also try the one called Emoji.