Hi,
if you want to add further points in adjustable distance and change the Garmin routing mode and do further changes, you can use the converter
https://gpx.shelms.de/GPX/GpxShaping.html
Help:
https://gpx.shelms.de/GPX/GpxShapingHelp.html
Thread about converter:
Converter Kurviger routes for newer Garmin / BMW Navis
Ciao Markus