Add functionality to support integrated mesh layer modifications in Scene Viewer

[GIS_Weasel]

There is currently no support for dynamically adding, or managing existing mesh layer modifications within a web scene in ArcGIS Online.

Image: a lovely integrated mesh layer with areas I need to cut out

Furthermore, mesh layer modifications can only be created in Pro, and shared online as a complete Web Scene (i.e. not a Scene Layer). This precludes sensible data management and versioning, especially since you can't directly overwrite a Web Scene. In my opinion the layer modifications should be associated with the layer itself, way similar to vector tile styles.

Mesh layer modifications are not directly editable even in ago-assistant. They are stored as an obscure json file associated with the Web Scene.

• Please add support to clip or mask mesh layer modifications via Scene Viewer in a user-friendly way, either by drawing custom shapes or using a polygon layer
• Please relate scene modifications to the Scene Layer in a similar way to vector tile styles
• Please also add support for doing this in a programmatic way via arcpy