I need a way to keep a verb invisible unless the object is open. Is the only way to do that by means of the creation of a second object, one that stays in invisible as an object until the primary object is open, or perhaps there can be an alias for a verb? What I really want is just a way to keep the verb attached to the openable closable hidden until the object is open.

If it's an actual verb, you probably want to disable the automatically generated verb list for that object. Then you can add the verb to displayverbs when the object is opened, and remove it when it's closed. Note that your verb will still need to check if it can be used, because hiding the verb doesn't stop the player typing it in.