I just looked at the doodle on my loop-pull-curtains and they are that pill-shape type with the lenticular opening on one side that are clamped closed over two beads on either end of the thread that has plastic beads at every regular interval with a tiny space for the thread  (nylon i presume)

building such a thing with 3d printer would be easy to expand it so it's a full pill-shape enough to embed a set of word-nuts in the middle of it like this, you could make it quite stylish and have one on every curtain with most of them being dummies with nonsense picked out from what was left over after you picked out your seed phrase from a 2048 piece pack to do a few of them

put the real ones in the last place you'd look even if you discovered they had these things and probably they get stuck discovering bogus nonsense and give up

or maybe better, just put nothing on the bogus ones so they don't initially expect to look for them after finding a couple with no inscriptions on them