Allow USING (geometries, etc.) of Custom Map Data, not just looking at it

[jidanni]

Description

Here we are tantalizingly looking at a Custom Map Data node that we want to insert into the map.

Alas, it is all just "window dressing".

Even if we promise to clean up the tags of the node after inserting it into the map we are not allowed to interact with it in any way. Sort of like we haven't earned that privilege yet.

The best we can do is try with our eyeballs to create a new node as close as we can.

Sure, you might say "Who cares? We never said the map should be "too" precise. Besides, I bet the data you usually create isn't too precise either."

OK, but what if I didn't create the data. The Bureau of International Standards did, etc.

See also #8503 .

Screenshots

[1ec5]

Related to #4164, although that issue was specifically about an ArcGIS FeatureServer, whereas this request is more general, for any endpoint or file format that iD supports as a custom data layer.