Display existing geometry when capturing new point/trace/shape on map

Yes, my apologies @Edmonds, we're still in beta and gathering feedback before release mid-July! You can find more information about the beta here.

That's right, the special geometry Entities column or form field can contain a mix of any of the geo types in ODK format.

Yes, same thing. Currently the functionality requires having a field named geometry in your repeat. You could coalesce values from different sources into that field and they could have a mix of geo types.

Sounds like you have some great ideas on how to leverage this, hurray!