Idea for extending this: keylogger (yeah, that's a downside...) that'll watch what you type, learn common phrases, identify common ones, then come up with shortcuts, then each time you type the full phrase it gently reminds you of the shortcut. Then anyone can install it, no friction, and over time it'll slowly start making you gently more productive.
Something like auto export slack history each week, get a word frequency. Then mantually assign a bunch of expansions based on what you see?