Have you ever run into a issue where the Trigger fields are not available in the Logic App Designer View?  

Check to see if your Request Body JSON Schema has  required fields

Only required fields will be available in the designer.  This is by design. 

TIP:  Use jsonschema.net to generate your schema

JsonSchema.net is a tool that automatically generates JSON schema from JSON according to the IETF JSON Schema Internet Draft Version 4. JSON Schema will be automatically generated in three formats: editable, code view, and string. To get started just return to the homepage and start writing some JSON in the textarea on the left-hand side.