Dress code?

There is no dress code per se in Switzerland. You can wear anything you want, within reason.

If you are asking about dressing for the weather, it depends on where you will be and what you will be doing. You can find detailed weather averages on several weather websites.

What will you be doing? i.e., hiking?

The Swiss cities will be quite warm, but the mountains will be brisk, with possible rain.
Layers are the answer. You'll be in country at a great time of year.
Enjoy!

You will for sure visit the mountains and therefore need one waterproof outer layer and other layers. Alpine weather is fickle. You may have sunshine in the morning and then hail in the afternoon, or vice versa.

No code, unless you are going to fancy restaurants or the opera, I suppose. We go every year. My dress up outfits a nice, dark, tailored jeans and a blouse and/or sweater plus a little jewelry. My husband a button down shirt or a sweater and sticks with his travel/hiking pants. We both have shoes that are not-hiking-boots for “dress up” and city wear.

Unsure of what you mean by "dress code".

Plan packing with the layering approach. Your days can be in the 80s and blue skies or cold and wet and everything in between.

With layers, a lightweight waterproof packable raincoat/jacket and a down vest/jacket or similar and you'll be ready for anything. Toss in a knit cap and gloves/liners for early mornings in the mountains. And a ball cap/sunhat for strong sun at high altitudes.

Footwear would be decided by your activities. Are you a walker or do you plan true hikes regardless of weather?

Thanks to all for advice. I feel more at ease now.

Wear clothes.

Wear clothes

Strictly speaking even that is not required, except in Appenzell. And there is an interesting story there...