Shift+T does not work at all in off-hand, armor slots and hotbar. It doesn't work properly (just shares item in first hotbar slot) in the creative inventory and any storage blocks, vanilla and modded, like chests, furnace, hoppers etc.

Quark: 3.3-373
latest.log

edit: only quark test
also, chests send the right slot number but from the player inventory instead of the chests inventory

latest.log