HI, Im following UnrealCGs advance IK tutorial，I open his project file and found he creates a subgraph in event graph, but I can not find out how to create Subgraph in 4.20.
Hey windlox, for this just select all nodes, right click and click collapse nodes button. Tadaa 
Ahh you are welcome. If you are problem solved, please click solved button for another people find to solution easily.
Thank you!