Ask HN: What is your favourite keyboard customizations? (qmk,system config)

For me the most useful customization I've ever found was to replace CapsLock by Esc. It is so ingrained in my muscle memory by now that I really struggle to use a keyboard when this mapping is not in place. I've always made this configuration via system options and it works really well. I was pleasantly surprised to discover this was a pretty simple configuration to set up in a mac, much easier than what I had experienced on linux. Recently I've started to dip my toes in the QMK world and was wondering what are some interesting 'modernization' I could apply to my workflow. I see a lot o people singing the praises of layered workflows, but my memory is not that great and I struggle a lot with the 'layout memorization' part. Maybe if I could print my own keycaps this would be easier. Do you have any customization ideas to share ?