Under File->Export, specify the surface that you wish to plot the variable on. Check the box “Line and Face Connectivity” under “Export Geometry Information”, and press “Save”. Edit the .csv file in a text editor or MS Excel. Add the variable name to the list at the top of the file, and the column of variable values that correspond with the (x,y,x) coords. Under File->Import, browse for the modified .csv file. The new surface will show up in the tree view (e.g. “Imported Plane 1”). Click on the surface to edit. Under Variable, select the new variable from the list (e.g. “Var on Imported Plane 1”) and hit “Apply”.