You can install an add-on, but since you're on W10, I suggest you use the emoticons provided by the Windowskey+. (period) menu in any application.

Except I don't know what that is.

See this informative article: https://www.computerhope.com/jargon/w/winkey.htm

Thanks!+

I've also just updated to the current version of Thunderbird, have a 64 bit pc, but can only download the 32bit version? Where are the emoticons, or why have the been removed??

I'm not about to start adding "add ons" to any software especially since they - the emoticons - were in the version they updated from, and now there aren't any?

I'm getting more and more dissatisfied with Thunderbird and Mozilla in general with all the changes they make and the deletions etc., when personally I cannot see any reasons for the removal of items we all use everyday in all platforms, email, phone txts, social and more. I've even recommended both email and browsers for many others using Office etc., and they have installed both programmes from Mozilla also. Might have to scrap both email client and browser and find something else I think. I'm not a happy camper, so why don't the developers put one of lifes simple pleasures back into the Thunderbird programme, if only to keep users happy?

The emoticons are still there in 78 if the Formatting Toolbar is shown in the html Write window (see picture). The W10 emoticon selection is much larger.

The 64-bit and 32-bit versions are available here. If you had 32-bit, the update would install 32-bit, but you're free to install 64-bit, although there's no significant advantage, and a few pitfalls.

I just took a look at the add on - the emojis in it are just as bad as the TB ones.