This feature was introduced in 0.9.22 version
The idea behind this feature is as follows:
For each track representation,
Default values :
(*) default map is the first published maps in the ordered list
If you defined a hillshade overlays in the map list, this layer is probably hidden by default (visibility set to false) because most overlays are not defined worldwide and should only be used in specific area. If you define this overlay as a default overlays, it will bet set visible automatically for the corresponding categories or tracks.