Let me get this straight....... You setup 50 Gmail accounts so that you can get access to 750GB of storage for free and now you're looking for a way to control all this storage from one account.
My first guess is going to be that it can't, but, maybe someone else can give you a different answer. Why not just get yourself a google one subscription that is attached to a single Gmail account? Where I'm at it's $13.99 per month for a 2TB plan but that price may differ depending on your location.
one.google.com
