Sorry for the delay in replying.
Thank you for all your suggestions.

@RussellJ This option looks very nice. But, I'm not sure about skipping Bellagio. I imagine how commercial can be, but I think it's worth a first visit. At least, once. But I see as a good option go to Pigra, funicular schedule permitting.

@Perche Thank you for all the details. They are helping me to plan my timetable better. I need to decide if I go east to Varenna or west to Argegno-Pigra or Lenno (@Alsacienne It is worth considering a visit to a villa; the guidebook talks about that). As you note, maybe Varenna is a better choice as it combines the possibility of both a hike and a beach.