File this under features I didn’t know existed! Credit to Paul Hayward in our consulting team for flagging this.
In Teams private chat or channel chat, you can press up arrow to edit the last sent message.
After I hit send, I press Up Arrow
I can then edit the message I sent
You could also edit a message by hitting the 3 dots to the side of the message and pressing edit, but up arrow is a really nice shortcut.
It turn out this feature has been in the client since at least February 2018, user voice reference.