the button I want most in my Typing English career: a "yes that's misspelled, correct it to the first suggestion" button.

having to switch to a mouse to click on the spellchecking for every minor word is so tedious

maybe if you hit it again after it applies a correction, it goes to the 2nd most likely suggestion
I'd have to pair this with a spellchecker that understands my personal english dialect of Later IRC English, though. Standard spellcheckers don't understand how I capitalize and think I misspelled words all the time, just because I didn't capitalize them.

one thing I'd really love to have is a better way to do text input, like have a single program I type into that interfaces with everywhere I type English*.

right now it's a bunch of website textboxes, chat apps, text boxes... a unified customizable & hackable frontend for typing would be perfect.

* as opposed to programming/shell/commandline stuff, not other Human languages. The only other language I know enough to ever type in is Latin, and that's fairly limited. I'm sure I can figure out "cinaedus sum" myself
a few replies mentioned IMEs: maybe I could implement this as an IME, which'd let me tie it into my operating system's keyboard support in a nice way?
my other option is just having it be an always running textbox app, that appears when I hit a hotkey. But crucially when it appears, it queries the running program and figures out where the cursor is, so when I finish typing into the floating textbox, it can paste it back into there.

having it as as a browser extension would also get me 90% of the way there since that's my main place I type, but the remaining 10% would be a pain.

and browser extensions are a pain, too

I have been programming in a lot of environments for a long time and I have long since learned to identify when you're developing for an environment that hates you personally and is always going to be an uphill nightmare of security, updates breaking things, and 3rd parties you have to wait on to approve anything
and those environments are never fun to code in. you should be getting paid to code for them, or they will rapidly burn you out.
(if you're getting paid, they'll slowly burn you out)
@foone I was going to say but you beat me to it. It really rots the soul to work with platforms that hate you. Some customers will do the same.
@tekhedd oh yeah. customers that hate you are also a bad one. even if the work itself is fine, having the response to every change you make being "I HATE THIS AND YOU SHOULD CHANGE IT BACK AND THEN DIE" can burn you out just as fast

@foone The most grateful *and* ungrateful were free software users IME.

And then there's big corps. "We are writing an internal app to replace you that steals all your ideas. Also we forgot to send the check."

It's enough to make you cynical, but the good customers are pretty awesome. :)