Alexa helper is a smart app which allows you to sign up to six different switches (they can be virtual or physical) to run a routine or change your mode. So that way you can say “Alexa, turn on party time!” And it turns on that switch which then runs a party routine you have set up in smart things.
If routines allow you to open your garage door, you would be all set.
You would set up a routine that opens the garage door.
You would use Alexa helper to run the routine when you turn on that virtual switch.
You would then be able to tell Alexa to turn on the virtual switch.
The only reason I didn’t mention this before, is, as I said, I don’t have a garage door controller, and I don’t know whether you can put one into a routine or not. It would certainly be the easiest way.
Here’s the link to the Alexa helper topic: