S&T 2010 to TomTom One XL

[kumo]

I like to use S&T 2010 to plan my trips on the desktop. How do I send the GPX file to my TomTom One XL? Thanks

TomTom units don't "understand" *.gpx files.
If the S&T cannot create *.itn files, you need to convert the *.gpx into *.itn with RouteConverter, ITN Converter or other tools.
The final *.itn file must be stored into the drawer itn at your TomTom device.