These seem to get created when you click the “Test” tab in the API Details page if no other M2M app is granted access to that API. This is what allows you to get the quick little code snippets and have them work right away as examples.
You can (seemingly) delete it, but it will recreate one if you click that Test tab again (again, if you have no other potential apps to use as a test). I suppose you could also just rename it to whatever you need it to be… that would work fine too I think.
I generally create my own applications that have access to that API and leave the test application as its own thing for when I quickly need to try something. It works out nicely.
** Keep in mind, I don’t work for Auth0, and only integrated over the last couple months. Just sharing my own observations 
So take this with a grain of salt haha.