JMP 13.2 gives you a bit more control over how the file is opened. Uunfortunately, it's not too obvious that you can control the behavior. You should be able to get what you need.
If the incoming file extension is unknown to JMP, we'll next check the file type drop-down to the right of the edit field. If that has a selection which is not ambiguous then we'll open the file assuming it's a file of the type selected. If the file type dropdown selection is ambiguous (ex. All JMP Files or All Files), we ask the OS to open the file.
So, in your case you can try this:
* Paste the URL
* Change the dropdown from "All JMP Files" to either "Text Data" or "JSON Data File"
* [Optional] You may want to un-check the "Select this filter the next time..." if you don't want it remembered.
* Click OK
The OS dialog will download the file to a temporary location with a crazy name like FSERXVJW with no extension. JMP will try to open the file with the kind you selected in the drop down.
I am interested to know if having the dialog download your json and opened with the "JSON Data File" choice is faster than the Open("URL","json"); route. We may have perf work to do in that case...
John