Created attachment 118786 [details]
My try to match UTF-8 emojis to KMail smileys

SUMMARY

In the composer window there is a "Add Smiley" button which only works when the message is being composed as rich-text format. Since UTF-8 is continually expanded with emojis and is supported by every self-respecting platform, my suggestion is to replace those smileys with UTF-8 emojis which would make them available for plaintext mails, too.

STEPS TO REPRODUCE
1. Compose a new e-mail
2. Disable rich-text format
3. Click the "Add smiley" button

OBSERVED RESULT
The button is greyed out and therefore doesn't work.

EXPECTED RESULT
The button unfolds a menu with a set of emoticons which are inserted as UTF-8 emojis when clicked. The recipient's client can display them without further interpretation (unlike classic smileys).

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 4.20.6/5.14.5
(available in About System)
KDE Plasma Version: 5.14.5
KDE Frameworks Version: 5.54.0
Qt Version: 5.11.3

ADDITIONAL INFORMATION
In the attachment you'll find some UTF-8 equivalents to the smileys in the Smiley menu, the ones I couldn't find are marked with X. The "tofus" are the one which are too new in UTF-8 and can't be displayed even using the Noto Sans font. Last but not least I added some suggestions which I think are used quite often and therefore would fit well.