Italy travel plan, should we add Varenna and Bellagio?

We’d be going to Europe later this year and would be doing 2-3 nights in Amsterdam first and then wish to explore Italy. We liked spending time in Florence and Rome last year so want to explore more.

We are thinking of going to Venice, Florence (with day trips to Siena and San gimignano), Rome. Not sure how we’d go from Amsterdam yet, but I was exploring a few ideas.

If we want to add Varenna and Bellagio, how should we make the itinerary? Should we add a few days in Switzerland as well?

Would really appreciate if you can share any experiences you have, that would greatly help us make the most of this trip, we might not get a chance to do it later for a few years.