Car rental Lake Como to Venice

Don't know where Bellano is, but you could get a ferry to Varenna and get a train to Milan and Venice. You could also get a bus or ferry to Como to do the same thing. Como would probably be the closest place to rent a car to drive to Venice.

There are car rentals in the city of Como. And good train service from there too.

What time is your flight from VCE?
I’d want to be in Venice the night before, not trying to drive from Como to VCE on da6 of flight.

Have you checked car rental rates? They are extremely high this year.

"it would take a similar amount of time."

Going to pick up the car in Como and all of that business will end up being longer and more costly than taking the train. There are no car rental companies in Menaggio. You would have to take bus/taxi/ferry to get to Como (where the nearest Hertz/Avis/Europcar locations are), go through the hassle of picking up the car, driving to Venice, refuelling before dropping off, and then dealing with the Italian tradition of them trying to fleece you for scratches and dents that were there when you picked up the car.

Take the train. Or even better, change your ticket and fly out of Milan

Ferry from Menaggio to Varenna (10 min crossing). Walk from the dock in Varenna to the Varenna-Esino train station. Then take the train from Varenna to Milano Centrale, then another train (fast train possibly) to Venezia. Venice has two stations: Venezia Mestre, on the mainland (this is closest to the airport) or Venezia Santa Lucia (in the famous historical center in the middle of the lagoon).

If you have a flight to catch, it is recommended you stay in Venice the night before, unless the flight is a late afternoon flight.

Renting a car (in Como) just to go to Venice makes no sense: more money, more time, more hassle.