Some time ago, i wrote some Klipper macros to pause a print and move the head out of the way, to allow a nut/whatever to be inserted, and then carry on printing. I recently needed to encapsulate some small neodymium magnets into some hooks, so that caution notices could be attached to metal clad switchgear. Easy enough, except as my printer nozzle is hardened steel, there would be problems trying to finish the print after the magnets were inserted. I have no intention of messing about with epoxy resins or glues for holding magnets to plastic. I've attached some code that produces small magnet holders, with a ring for attaching thread/wire/whatever. It will take any size cylindrical magnet, needs no supports when printing, and once the magnet is inserted, then the plug is a snug fit and can be pressed in with pliers. The wall thickness and clearance values are fine for my printer, using PET-G filament, but may need to be different for a more brittle material, such as PLA. With a layer height of 0.2 or 0.28 mm, and 0.4 mm nozzle, it only takes a few minutes to print. Print them  solid (in Cura, setting  'wall line count'  to 50, will do that good enough). Have fun measuring your magnets using steel calipers 😉