GGU-3D-TRANSIENT: "Save nodes" menu item

After selecting this menu item you can save defined hydrograph points in order to have them available again at a later date. For reasons of clarity, it makes sense to use ".knt_3d" as file suffix, as this is the suffix used in the file requester box for the menu item "Times/Load nodes". If you choose not to enter an extension when saving, ".knt_3d" will be used automatically.