In RouteYou and some GPS cycling computers like the Mio Cyclo it is not possible to reverse the direction of a track. This can be solved very conveniently with the program ReverseStravaGpx.
Go to https://sourceforge.net/projects/reversegpx and download the file ReverseStravaGpx.exe.
Open the file with the explorer, the program asks to select the gpx file on the PC.
A new gpx file in reverse direction is created with the addition +R+.
For instance:
Maastricht-Spa.gpx
Becomes:
Maastricht-Spa.gpx
Maastricht-Spa+R+.gpx