However, you don't have to do anything special for that, just put in waypoints for the scenic parts of the route and the distance in between will be calculated using the fastest option automatically anyway, no need to place waypoints on the motorway for that. See this example:

I explain better my need. I make a journey that in part I want to be a motorway because the normal road is too long but then, when it's convenient for me, I want to leave the motorway and continue the journey on the normal panoramic road. This is a very common situation in Italy, Croatia, Southern France and Spain

That's a common situation everywhere I guess... Any GPS device I know takes you to the start of the route the quickest way anyway, so it does not make real sense to adapt the route to your starting point anyhow. Just leave WP1 at where the panoramic route starts.

@Giuseppe-Marino-0 @Steve-Lynch Even better (worse?), I usually don't bother creating a route in MRA for parts of the journey that are just the quickest way to get somewhere.

For example, I often have single-day drives following this format:

1. drive from home to the starting point of the actual drive
2. do the actual drive
3. drive home from the end point of the actual drive

For 1 and 3 I don't bother creating a route at all. I just enter the location of the start of the actual drive for step 1 or my home address for step 3 and let my navigation app guide me there using the fastest route. For step 2, I'll have a fully planned route loaded, because that's when I care about the roads I drive, not getting to and from it.

Very correct.

Perhaps even easier:

I create a route with starting point where the planned route actually starts. I start the route at home and tomtom guides me over the fastest route to that start point.

For example, I often have single-day drives following this format:

1. drive from home to the starting point of the actual drive
2. do the actual drive
3. drive home from the end point of the actual drive

For 1 and 3 I don't bother creating a route at all. I just enter the location of the start of the actual drive for step 1 or my home address for step 3 and let my navigation app guide me there using the fastest route. For step 2, I'll have a fully planned route loaded, because that's when I care about the roads I drive, not getting to and from it.

Or you could just ignore all the OSM faff with Segments, and just manually create the route you want directly in the Here map.

Segments are explained in this video.