Is there a way to force a Kurviger route on the Motorway?

If you want to use the motorway in parts of your route but want to use curvy routing in the rest of the route you might want to set the fastest route for parts of your route, for example from the start to the first waypoint. Click on the waypoint and then select the fastest route.

For only very short passages you can place a shaping point on the motorway. Right click or tap on the map where you want to place the shaping point. Note that most motorways have two opposite lanes. It is important to place the waypoint on the correct side, if the result looks weird, you can try to move the waypoint to the other lane.

If you want to enforce a whole route on the motorway, you can use the fastest route, this should already result in a high likelihood to end up on the motorway. If this is not enough for you, you can try advanced settings like avoid main roads and avoid narrow roads to further force Kurviger on the motorway. This should result in a mostly motorway route unless there is no reasonable motorway along the route. Make sure not to select avoid toll roads if toll charges incur on the motorway in your country.