It's possible they'll add the ability to assign an input as a stinger, both to shortcuts and in the API.

That is, being able to assign Input1 to use with stinger1.

It would help to quickly change which one to use; there are four, but they aren't enough if you're running multiple continuous events with different themes.
They're not only used as transitions but also as background images (LED screens). It's a very good way to open or close them given the movement that can be achieved with GTZIP graphic transitions.

Also, the vmix XML (http://localhost:8088/api) should include the values ​​for which input each stinger is assigned, allowing you to read the data and execute tasks.