Instead of exporting/importing your tracks you can copy/paste
them outside the imported file.
This is the only way to make them displayed above the rest, because the imported placemark files are displayed before all other single items.
Then single items are displayed by types (in this order: areas, routes, tracks, set of waypoints, waypoints), and for each type they are displayed in the order they have been added. There is unfortunately no way to change this.