How to do an em-dash in QMK and ZMK keyboard firmware

It’s time to reclaim the em-dash. A common refrain is that the use of an em-dash in writing is a clear sign sign that it was written by an AI (or an LLM). This kills me. Up until really very recently, the use of an em-dash in writing was a clear sign that someone knew how to use punctuation (as was the use of a semi-colon). I have always been a big user of em-dashes, mostly for parenthetical comments, which I tend to do a lot because that’s just how my brain works. Actually the more accurate truth is that I use a lot of en-dashes as em-dashes, because typographically I like how they look better, but I do this by preference, not because I don’t know what is correct. Inserting an em-dash (shift-option-hyphen) or an en-dash (option-hyphen) on a Mac is both easy and mnemonically-consistent. Doing so on Windows is neither of those things. As such, I’ve always programmed my keyboards to make it easy. Here is how you do it (or how I do it, anyway) on the two major open-source keyboard…