Train from Venice to Murren

You don't actually change trains in Domodossola, that is where the train crosses from Italian railways tracks, to Swiss Railway tracks. The train crews change over, and Italian ticket pricing applies up to Domodossola, and Swiss ticket pricing thereafter. You just stay seated and look out of the window.

• The Italian railways site ( www.trenitalia.com ) will allow you to book any train in Italy, and any train crossing the Italian border. So you can book here from Venice to wherever you first change trains in Switzerland, Brig or Spiez.
• The Swiss railways site ( www.sbb.ch ) can also book trips within Italy. So you can book Venice to Mürren here. But this site does not have all the discounted prices for Italian trains.

I would consider the following strategy:
(1) Price up Venice to Mürren as one booking on www.sbb.ch
(2) I would then price up Venice to first change of trains in Switzerland (Brig or Spiez) on www.trenitalia.com , followed by the last leg to Mürren on www.sbb.ch
Choose whichever is cheaper.

Note, within Switzerland, you do not need to reserve a seat, just buy a ticket. All tickets are valid on all trains. On Italian high speed trains you must have reserved seats, which come automatically with the tickets, and the tickets are only valid on that one train.

Cinque Terre to Florence can be bought on the day or in advance. A pass would not be god value.

Whether a pass or half price ticket is worth buying for Switzerland depends on what other train trips you are planning in Switzerland. You would have to do the arithmetic yourself.

Depending o your plans in Switzerland, some kind of pass or Half fare Card will be an option since Swiss trains are rather pricey, but necessary to get around because they cover discounts on most mountain lifts as well. Also Switzerland operates on a miles-traveled pricing model with no advance purchase discounts.
Italian trains are usually best with advance purchase fares on fast trains, and purchase regional trains at the station as needed.
You might find a discount fare from Venice to Spiez as EC trains from Italy pass through there.

A couple of departures per day with 2 changes to Interlaken - Milan and Spiez. Best total journey approx 6 hours.

A decision on a Swiss Travel Pass or Half-Fare Card is based on everything you'll do in that country. So what comes next? With either one, yes just a ticket from Venice to Domodossola is all you would need to buy from www.trenitalia.com or an Italian train station.

With a Half-Fare Card, you'd buy the ticket for the Swiss portion of the route from www.sbb.ch (one ticket; they can figure the connection points); or with a Swiss Travel Pass you'd be covered all the way from Domodossola to Muerren without buying a separate ticket or reservation.

Your last thread mentioned Paris but I assume that you'll fly from there to Pisa or Florence (www.skyscanner.com) and are not using a multi-country rail pass.

On Italian high speed trains you must have reserved seats

It's been a few years but in my experience you also need reserved seats on the trains crossing the Italian-Swiss border regardless of whether they're high speed trains. Try to do this in advance - it's stressful to deal with Italian bureaucracy, even at the ticket window, when you've got a train to catch.

ak,

In order to suggest ticket options, it would help to have some idea on your order of travel from Cinque Terre > Florence > Venice > Mürren.