Other than Berner Oberland, Lake Geneva, Appenzell, Zermatt where should I go 4 nights

Luzern perhaps?
Or the Engadin, e.g. Pontresina or Samedan. Depends on what you're after and on your tolerance for long-but-scenic train journeys.

Well this is the trip where I finally do the Bernina Express route using just regular trains. I'm flying back from Milan.
I might go up Pilatus weather permitting. I've been up Mt Rigi already via Lake Lucern. I'll have a 4 day Swiss Travel Pass.

Are you planning to stop in Engadin while travelling the Bernina Express? It is worth a couple of nights, in my opinion.
What's your rough planned route in Switzerland so far?

I am flying from Amsterdam to Basel lookin at staying in one town (that might have some evening entertainment) 4 days and daytrips not changing hotels

Pontresina, charming town, near St-Moritz.

Ok I'll give Pontresina a try thanks

Ah I had misunderstood then. I thought you had 4 extra days in your Switzerland schedule, not 4 days total. Doesn't really change the recommendations though.
Luzern has tons of day trip options, but since you are planning to take the Bernina railway, Pontresina makes a lot of sense (it sits on that railway line), and I really like that corner of the country.

This looks like a wonderful list of places to see in Switzerland but I don’t see how it could be done as day trips from a single base. Especially not with only 4 days.

From arrival in Bern, the Appenzell and Lake Geneva (Lausanne) are in opposite directions. The Berner Oberland (Laterbrunnen) and Zermatt are reasonably far apart and both deserve more than one night and certainly more than a day trip. Then you need to get to Chur or St. Moritz (Glacier Express route from Zermatt) for the Bernia Express route to Tirano, Italy and onwards to Milan.

Maybe you could do a loop route with a focus on riding trains and a new hotel each night. But with 4 nights you may want to reduce the number of places.

Enjoy the planning and the trip!

Beth I had already been to those places and was looking for some where else and have decided 4 days based in Pontresina exploring the region Engadin where I have never been.

Ahh! I had misunderstood your question. Pontresina is a perfect base for 4 nights. I’m still dreaming about our 2020 Switzerland trip that never happened.

Enjoy your trip!