Preselection for multiple tracks

I’m still impressed by the rich feature variety of this great tool.
Lastly I was trying to integrate several *.gpx tracks in one map, which works perfectly fine and even the file box selector ist displayed. Though I was wondering if there’s any variable, which I don’t know yet, defining which track(s) will be shown before any user interaction has taken place. Currently it is always the first track in the file list, but I was wondering if I can set this individually (e.g. the third track will be shown as preselection).
Thanks for your help or hints!