After a bit of searching I found out with the swing program node service you can interface directly with the program api to build directly program nodes.
Is it possible to add under a move node(e.g. MoveL) a waypoint node and give it a customized name
Yes, it is possible! I will recommend you to take a look at the EllipseSwing sample that can be found here: GitHub - UniversalRobots/EllipseSwing: URCap sample that mainly demonstrates the principle of RobotPositionCallback, WaypointNodeConfig and PoseFactory
It is also available in the SDK and StarterPackage