Driving Tour Milan-Bellagio to CT, Tuscany, Umbria & Rome

Well only you can decide if you want to replace one of those areas with the Amalfi Coast, bu I would not go to both Cinque Terre and the Amalfi Coast. While there are of course differences, both are coastal beauty spots, great for hiking, both with abundant crowds.
My one travel dogma is to maximize your time, and if flying into Milan and out of Rome, I would concentrate on areas between those two.
A car is not great for Cinque Terre.
What areas of Tuscany and Umbria have you identified?

I have not figured out Tuscany or Umbria yet. Any thoughts/recommendations?

Have heard I should also visit Gubbio or Orvieto.

Both are such vast areas, I just meant you should flesh that part out first.
I have never heard a bad word about anywhere in Tuscany. I have enjoyed the northern and southern parts of Tuscany. Not yet to Umbria. It's hard to go wrong, but if you are going to drive, be sure to choose places that make the most of having it.

This looks like an excellent itinerary to me. Umbria seemed less crowded than Tuscany; we have enjoyed both provinces. In Umbria, Spello makes an excellent base.
Save Southern Italy ( Amalfi Coast, Capri, Sicily) for another trip. We didn’t travel south of Rome until our 7th trip to Italy.
We parked our rental car the whole time we were in the Cinque Terre, in a large lot in Monterosso where we were staying. You also could stay in beautiful Santa Margherita Ligure and do a day trip to the Cinque Terre by train.

Wiki: Thank you...can I ask where you stayed in Cinque Terra? And did you like the accommodations?

Also be cognizant of time of year--parking is likely to be quite scarce in late July.

I will join the others who advise against trying to cram a visit to the Amalfi area into this trip.

You can get to Lake Como and CT via train. Pick up rental car when you leave CT and not have the expense of having to park it.