Pluggable Widgets - Microflow/Nanoflow Return Value and Parameters

I’m trying to call a microflow in the new React-based pluggable widget. I’ve found that the microflow/nanoflow property types have been replaced by the new action type, and the microflow/nanoflow can then be used by calling .execute() on it. This works for microflows/nanoflows that don’t have a return value, but what about ones that do. How am I supposed to access the return value of a microflow/nanoflow? I also don’t see any way to pass in parameters to the microflow/nanoflow such as the old way of using a GUID?