"I would like to have a single line selected, with multiple elevation surface layers in the profile graph."
- That will not be possible, only elevation surface layer at the time: 1 ground layer + 1 mesh/scene layer. Like here: sample.
"I assume this would only be for selecting an existing line; not interactively drawing a line using the widget."
- Both. If there are line features in the map as well, you can select them and it will show the ground elevation profile, the mesh profile and then the profile for that selected line if Advanced settings are enabled.
"When is the next update expected to be released?"
- End of February for ArcGIS Online.
"In this update, would I be able to switch between each 3D mesh or scene layer from the same widget?"
- No. Only one 3D mesh or scene layer per widget. Example (note this is still a work in progress and display is a little off):
There are 3 sources of elevation here:
- The ground elevation (brown) - use the default or define your own
- The mesh buildings layer (pink) - this would need to be your groundwater surface elevation scene layer
- The line feature layer with elevation values (red) - this is the selected line to render this graph