Can monsters use weapons they took from player characters via Disarm?


Without necessarily getting into whether or not Disarm is a waste of time or not, if a monster Disarms a PC, (page 271, DMG) can that monster use the weapon if it picks it up?

Example…

A Bandit Captain uses its first Melee Weapon Attack to Disarm a PC of their magic sword… then a free action to interact with an object to pick up the magic weapon, and its second Melee Weapon Attack to attack the PC with its new toy, the PCs former weapon?

Multiattack is specific to certain weapons sometimes… can monsters use other weapons not listed in its multiattack?