Those fields in the piping input are for external structures that impose displacements on nodes in your model, such as equpiment nozzles. They are rarely used for piping otherwise. Perhaps you might want to use them to analyze a maintenance issue where you broke a flanged joint and wanted to see if pulling the joint far enough apart to insert a paddle (for isolation of a part of the system) would cause permanent damage.

Don't worry, the system will otherwise calculate its own displacements - you don't have to calculate them!