Overturf wrote: … how to hide a lavalier? … inside the tie-knot …
when I was in charge for some gameshows, decades ago, we did the same: from inside the shirt, from the top, into the tie-not; Lav points to the ground, but doesn't matter, those are omni-directional.
Or… if no tie:
taping it into the collar, but putting some tiny 'Dead Cat' over the mic to avoid rustle.
And when our 'Venna White' wear again a dream of nix of cloth, we used a technique, which is in use on Musical stages: a very tiny Lav capsule (you gettem in flesh-tone for this purpose) and glue it (Mastix) onto the front-head/hairline.(cable to the back, hidden in hair), transceiver attached to bra… Our dress dept. sewed a tiny pocket for that.