Are custom property binding types supported by the SDK? AbstractPropertyAdapter, BindingType, BindingConfiguration, and openBindingDialog seem relevant but I’m not sure where to start. I only care about Vision (if that makes any difference).
Or should I just try and build my functionality into an expression function instead?
Adding an expression function will definitely be easier. There’s even an example for it in the GitHub repo.
I don’t know if we’ve ever even considered bindings to be extensible.
There's very limited extensibility, and it is effectively handcuffed to the same functionality as expressions. I would love to have extensibility that would allow a true asynchronous binding with configurable parameters, like the existing Named Query binding.