DYNAMIC NODE: I am using EPANET 2.0 to model a huge water system.

DYNAMIC NODE: I am using EPANET 2.0 to model a huge water system. I've attached an image of the latest and greatest water system just to show the size (I know there are still elements missing such as reservoir, pumps, tanks). I drew the system in CAD and brought it into EPANET using EPACAD. I had to add a break in each poly line at each valve location in order to model the valves in EPANET. I am going to have to add valves and pumps when survey and remaining as-builts are received. ***If I want to add a valve in an existing pipe already modeled in EPANET, I have to add a node in the middle of the pipe. I can't figure out how to add a node that is linked with the existing pipe. When I add a node it isn't dynamic. How do I do this? Thank you!Also, How do I "undo" in EPANET 2.0?