I wanted to create fidget keycaps for friends and none of the ready-made alphanumeric keycaps really did it for me so I found a very well-designed flat-top keycap by 3DNERDCAVE (https://www.printables.com/model/118708-simple-cherry-mx-keycap/files) and just used Bambulab to overlay letters and numbers on top.

My original remix had the lettering higher (embossed) on top of the keycap as I didn't have my P1S at that time and it was the only way to have it work with manual filament swaps on my Ender 3 v2. Now that I have my P1S, I made it flush with the top. Having it higher than the keycap is just a matter of increasing the letter height in Bambu studio.