Is it possible in v5.0 (I am using 5.0.11733.9347 for Windows) or in a later version?
Google Groups question This application needs the ECLIPTIC seems to indicate it is not possbible whereas Using Google Earth's Sky feature in your classroom says "Use the Constellations layer to examine the concept of the ecliptic" (this is not very clear and does not explain how). I have turned on the Constellation layer, but the ecliptic does not show. It should be a line from the upper left, through the center and to the lower right of this view:
Perhaps it is possible. From Google Sky: hands on, plus Top 10 uncommonly cool sights:
Yes, the bright curve is indeed the galactic plane and the fainter one the ecliptic.