I am looking at a mashup looks like carried forward from previous version of ThingWorx. I started working learning from 9.3. Not able to find any documentation. Can I get information how ThingName is configured? .
Your screenshot is showing a mashup with a mashup parameter and from somewhere, not shown the parameter value is provided.
My best guess, since it is called ThingName, there is some other service or parameter or selection in a parent mashup, that is providing a default or selected Thingworx Thing.
Like loaded events which gives output in the same way Thingname is property, not able to see the binding, neither it has been configured in mashup property tab.
I'm not sure if you've considered taking the ThingWorx fundamentals courses, but that should give you enough basis to understand Mashup parameters and the concept of 'dynamic' services used within a mashup, which is most likely why the ThingName is being passed in.