HA entity msg.payload options?

Here is my basic question: How do I find the payload options an entity will receive in home assistant?

As I stated above, I am using home assistant to control all of my devices and have the node red add-on installed for advanced automations. Through trial and error, and using "get current state" debug info, I was able to figure out I can send these payloads for lights:
msg.payload.service = turn_on
msg.payload.data.transition = "input seconds to turn on"
msg.payload.data.rgb_color = [255,0,0]
msg.payload.data.brightness = 0-255

How would I have known these before hand? Ultimately I am looking for garage door ("covers") payload options but, is there a list of msg.payloads somewhere for all the various entities? Tried searching and found pretty much nothing.

I am able to open my garage through home assistant and apple homekit (using HA's homebridge). I have tried various payload messages and all failed. My issue is, how do I have node red tell my garage door to open? And that led me to my main question, how do I find the payload options for "fill in the blank" entities?

Thank you for any direction.