Unfortunately SmartThings doesn’t do this anymore.
I had done the same as you a long time ago and had the remote and sensor in one. But now you can’t do that now. All you can do is have a ST Multi setup as the sensor on the door to measure door orientation, hack the existing garage remote or wire the Linear relay to the push button port on the garage door and change its attribute in the IDE to momentary button and have a cut off smart plug to kill the power to the garage door opener when not needed. What you can do to automate your plug and the remote control is setup a routine in WebCore to push the remote button a few seconds after the smart plug is turned on. I have this now.