What's your wish for? Navigating the chats more efficiently, or simply typing the messages? If the latter, why haven't you figured out a workflow where you do all your typing in Emacs, or whatever your choice of an editor is?

I have done that years ago and I just can't imagine my life without this feature. I never even try to type directly, anything longer than three words - in Slack, Browser, Teams, Outlook, whatever. There are packages like emacs-everywhere, but I don't use that. My technique is simple and I usually get it to work on every WM and system I use. It basically simulates Cmd|Ctrl+A & Ctrl+X, and via emacsclient opens a dedicated buffer and sends the text+PID. When done, pressing a key copypastes the text back into the app of the PID.

I can't recommend that enough - being able to use all the tools you have in your editor - completions, spellchecking, thesaurus, etymology lookup, translation and dictionaries, search of all kinds, etc., is absolute and pure joy.