Reactive Visual Scripting Behavior Tree Tool for Unity 2018.x+
Visual Scripting Behavior Tree Tool for Unity 2017.2.x+
GREAT Introduction to RX here! (introtorx)
Another one (with shiny marble diagrams!)! (ReactiveX.io)
Great List of Tutorials (ReactiveX.io)
Interactive marble diagrams! (rxmarbles.com)
This is all done via reflection, so they automatically show up!