The recent Shapespark release adds support for importing additional properties via a JSON file. The format of this file is described here: GitHub - shapespark/shapespark-extras-json: A JSON file format that can be used to import additional properties to Shapespark.
We won’t be able to work on exporting such properties from 3ds Max in the September (we started work on Revit), but if someone would like to work on such exporter we can help with any issues on Shapespark site.