Lauterbrunnen to Bolzano, Italy, by train?

Looks like the shortest route is 7 hrs 46 min so personal preference. I think it’s fine to do in 1 day. Might as well just get where you’re going instead of prolonging the travel. For times, see sbb.ch

Well, there are no straight forward connections but it would be possible to do it in one day.
https://reiseauskunft.bahn.de/bin/query2.exe/en is always a big help to find Europe wide train connections.

There are several connections per day, that take 8 to 10 hours with 3 or more train changes.
Routing is via Milano and Verona or via Zürich and Innsbruck.
It’s on you and your overall plan if you want to spend a full day in transit or if you break it in 2 pieces.
On the Italian route Stresa on Lago Maggiore or Milan would be options for a break. On the Austrian route how about St. Anton am Arlberg or if you are an adrenaline junkie you could stop at Ötztal Bahnhof and visit Area47.

Thank you for the advice. I think a day on trains watching the scenery could be pleasant. But I keep thinking a rental car makes more sense, and a car could be useful in the Dolomites. We'd really hoped to avoid car rental, however.

Renting a car will typically not make sense because it will force you to return to Switzerland to return the car, unless you fancy paying several hundred dollars in drop off fees.
If your itinerary involves going back to Switzerland, then yes, it could make sense to rent a car.

Okay, nix the car rental.

We originally planned to ride a scenic train from Switzerland to Italy but someone on another thread suggested taking a regular train that uses the Treno Gottardo route. Seems like a pleasant way to get a scenic train ride while spending a day traveling from Point A to Point B. Can you recommend how to book that route on the SBB site? The only way I can figure out to do that, and avoid being routed through the tunnel, is to indicate Airolo as "via" on the Timetable/Ticket Purchase page. I am using Varenna as a destination for an overnight before heading up to Bolzano the next day, but am open to other suggestions for a convenient place to stop over on Lake Como (or Maggiore?).

I've also looked at the route to Italy via Domodossola and Milan, but it perhaps is not as interesting as the Treno Gottardo route. Does the Treno Gottardo have better food opportunities, too?

I sincerely appreciate the advice from this forum. I'm struggling with planning this trip...our first to either Switzerland or Italy, and our first using trains as much as possible.

Trying to get to Varenna and add in the Gotthard line is really making things complicated. Look at a map, and you will understand. And then from Varenna to Bolzano is complicated as well...

You will need to decide what you want.

The best route, if you want to balance uncomplicated with scenic is to go via Zurich and Innsbruck.

If you want to include Treno Gottardo and lake Como I would stay overnight in Como town itself. That way you could indeed do Lauterbrunnen - Luzern - Como (via Gösschenen) on day one, and Como - Bolzano on day 2.

The Arlberg Pass train from Zurich to Innsbruck is noted as scenic. Kinda direct, too. Once at Zurich, take Arlberg Pass train to Innsbruck, then Innsbruck to Bolzano.

Link to Seat 61 description: https://www.seat61.com/trains-and-routes/zurich-to-innsbruck-via-the-arlberg-railway.htm.

We have done that transfer both directions and both spending a night in Milano as well as pushing straight through. Our preference, as much as we like Milano, is to push through and have that extra night at the other end. We leave as early as possible so we are settled by dinner time.

Are you staying in Bolzano or going on from there?

I have only done this in a single day, via the Zurich-Innsbruck Brenner Pass route.

Looking on bahn.de, your shortest options are 8 hours with 5 changes via Brig, Milan, and Verona; or 9 hours with 4-5 changes via Zurich, Innsbruck and the Brenner Pass.

Look at the Swiss rail map to follow the various route options:

https://cdn-doc.myswissalps.com/docs/default-source/rail-network-maps/swisstravelpass.pdf?sfvrsn=7788603a_56

Going via the Gotthard route, either with the Treno Gottardo or the deep Gotthard tunnel, requires travel north to Luzern at the start. So does the Zurich—Innsbruck route.

Varenna is not on the way on any of these options; it is a detour from Milan. If you want a to break the journey with an overnight on a lake, your options include
(1). The Gotthard route with an overnight in Lugano or Locarno (endpoint of the named Treno Gottardo), or the town of Como on Lago di Como

(2) the Brig—-Milan—-Verona route, with an overnight either at Stresa on Lago Maggiore or Desenzano or Peschiera on Lago di Garda. Or, if you really want Varenna, detour there from Milan ( one hour by train each way).

Thanks, everyone! You've given me lots of great ideas to explore.

I really am a newbie at working with the train schedules. I'm having trouble figuring out how to use them to select particular routes such as Arlberg Pass or the Gottardo, other than plugging in a "via" town that I know is along the way. I wish I could plug in more than one place along the way to get the particular train route that I want.

And I have not yet figured out where we will stay in the Dolomites; that is for a different forum page. For now I just want to know when we will get there so I can plan our itinerary going forward.

I think I've got it figured out. Thank you all, again!