To my understanding, the tool in your first screenshot is used to broadly say what kinds of things you want to parameterize in your ARM templates. I.E. "Parameterize the trigger property interval
of all triggers" , not "Parameterize the properties of this trigger only, excluding all all triggers".
It is not for defining entire triggers.
For example, my different environments use different storage accounts, so I would want my event trigger to point to different accounts (scope property).
To remove the default value of the scope (and force me to enter it so I don't forget), I would use:
Then in my arm_template_parameters.json
I see
},
"EventTriggerTemplate_properties_typeProperties_scope": {
"value": ""
}