Planning a route from Greece to Spain

[Nikolaos I.Paschalis]

Hello all,
I am planning a route starting from Greece, passing to Italy by ferry, and then crossing the west coastline of ITALY (cinque Terre, etc.) and continuing through Italian riviera - Monaco - France riviera and end in Barcelona.
What is the correct way so it can keep me always coast to coast (ss1)and not the below (bigger roads - attached pic)
Is it better to manually add waypoints one by one, or is there any other way?
Regards
Nikos

[Hans van de Ven MR.MRA]

@Nikolaos-I-Paschalis

Plan for every day a route.
Starting- and end point.
Add points on the road you want to drive