GGU-3D-SSFLOW: "Default depths" menu item

The default depths defined in this dialog box are assigned to all new FEM nodes defined using the "Mesh(x/y)/Define nodes" menu item.

If you edit the given z values and leave the dialog box using "Done" the newly defined depths will be adopted as of this moment for newly defined nodes. If nodes are already defined, they can also be retroactively assigned the new depths using the "For all" button.