The multiple querystring is now supported for all endpoints. Here is a curl example for creating two circles
curl -H "api_token: steve@mcneel.com" -H "Content-Type: application/json"
-d '[[{"X":1.0,"Y":2.0,"Z":3.0},12],[{"X":1.0,"Y":2.0,"Z":4.0},30]]'
https://compute.rhino3d.com/Rhino/Geometry/Circle/New?multiple=true
Results are just returned as a json array. I didn’t take the time to do any optimizations on the server for this, but I plan to. multiple calls for things like intersections should really be done using tasks for each item in the input array. This is not implemented at the moment and everything is very serial on the server.