ServiceNow has a very intuitive way to let you select what variables i can use in automations(they call it flows). it shows for every action what variables it has an you can drag and drop them in your next action.
what do you mean “variables” for every action. All actions have a config associated with them and all fields are available for use.
Are you referring to templates?
My guess is that OP is talking about templates, and specifically being able to know the structure of the trigger variable given a particular type of trigger? It is a little clunky to have create an automation, force it to get triggered, then go look in the changed variables section of the trace to see what data is available and how it is structured.
Maybe some examples in the documentation would be helpful.