Has anyone ran into the need to compute a ESRI JSON Geometry polygon field in Manifold? I can start from Manifold Geom, WKT, or Geojson. Although I ultimately need it to be a field in my table, it does not appear to be a format option for export (unless I missed something)

Any guidance or help will be greatly appreciated. Thanks!

There are libraries that do this, eg: terraformer/arcgis.

Where are you getting ArcGIS JSON data from? Usually you are getting it in the context of a web page, so then you transform it (using some Javascript library) into something more generic and store that.