Day trip from Italy into Switzerland

Where in Italy will you be for this day trip?

We will be coming north from Umbria….no specific destination as of yet but thinking Lake Como.
Unless there is a preferred place to enter.

If you will have the car and a few days, I'd drive up to the Zermatt area.
If you will stay in Lake Como (with or without a car), then others can advise on the train options. There are many, but I have never been able to get them quite sorted.

If you’re planning to go from Umbria to lake Como then you could always visit Lugano for a day trip. Similar scenery to lake Como but still Switzerland. From Bellagio or Varenna you can ferry to Menaggio and take the bus or taxi from there to Lugano.

I am from the States and I fully understand the distance issue. As I said, our schedule is wide open so we could work our way north from Umbria, with an ultimate destination that will get us to a train into Switzerland.
I wasn’t thinking day trip from Umbria.
But your comment reminded me of my cousin from Rome coming to the states (home base being in Pennsylvania at our home) on her honeymoon. She said, “We would like to go to Disney World, Niagara Falls and Yosemite.”
Ha! We responded….”No is possible! Not quite like Europe!”
They did get to fly to FL and then drove to Niagara Falls.)

To use many Swiss roads your car will need a vignette (sticker) that costs 40E. The tunnels are also quite pricey. If you don't have airline tickets yet, it would be much more efficient in time and money to land or depart from Switzerland and use the train for the Italy-Swiss leg.

I will be in Varenna for a few nights in mid October. If the weather is nice, I am tentatively planning to do a day trip on the Bernina express like (but on the regularnon-reserved regional train) from Tirano to Pontresina and back, spending a few hours in Pontresina or other stops. From what I have read in the RS Switzerland book and from various posts on this forum, it sounds like this should be very doable.

A rental car will probably not be the most cost effective option, as it will be sitting a lot of the time and you'll be paying for parking. As you may know, each driver will require the compulsory International Driver's Permit which is used in conjunction with your home D.L. You'll also have to be extremely vigilant to avoid the ZTL (limited traffic) zones that exist in many cities, as there are hefty fines for each pass through them.

Rather than Lago di Como, you might consider Lago Maggiore and the town of Stresa, as it will be easy to take a day trip from there into Switzerland. Take the train from there to Domodossola and then the scenic Cento Valli railway to Locarno, CH. While there you could tour around this beautiful city, buy a neew Rolex watch at the luxury Bucherer store try your luck at the Casino or take the cable car to Cardada/Cimetta for spectacular views - https://www.cardada.ch/en . Take one of the boats back to Stresa in the evening and enjoy views of the towns from the water. I've done that trip a couple of times and I always enjoy it. Be sure to take your Passports, since you'll be in a different country.