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In addition to the template, model (and optionally position), you can add other parameters if you want. They will be returned by the Narrative API, but will be fixed (so they will always be returned in the same way for the same Layout Block).
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2. Define the dynamic parameters
3. Define the JSON SCHEME
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After creating your JSON SCHEME with the jdorn editor demo link and confirming with the preview of the generated form that it is valid and appears as you would expect (remember, this will be the form which will appear in the Narrative Editor for the marketing department), you can copy & paste it in the dialog in the JSON schema textarea (as in the image above).