GGU-3D-TRANSIENT: "Linear sources" menu item
After going to this menu item you define a polygon by clicking 4 points anti-clockwise. The element nodes having their centroid within the thus marked quadrilateral are assigned a linear source with the user-defined value. If an element lies entirely within the quadrilateral, the corresponding nodes are not assigned a linear source.
If you need to delete existing linear sources, define the polygon again and enter 0.