It can be fun to go up the mountains in April. If the weather is still good for skiing, then the ride up might be crowded but once you are on the viewing platform you will be one of the few up there.
Last April I went up First mountain in Grindelwald mid-morning. No line up - I was the only one in my gondola and the ones in front and behind me were empty. There were some people on the Cliff Walk, but not many. The outdoor seating at the restaurant was equally empty. It was a stunningly beautiful day, I watched the paragliders taking off in the snow. The First Flyer and Glider were both operational.
I have also taken trips to Gruyeres in April, or the Morges tulip festival. This is a small event, compared to other countries, or what I was used to in western Canada, but beautiful.
https://www.morges-tourisme.ch/en/P91876/tulip-festival-2024
As the snow melts and the rains come the waterfalls become very powerful. So going to Giessbach Falls or Beatusholen, or walking the Lauterbrunnen valley is wonderful.
April is blossom time. You can read about various locations on the Switzerland tourism site.
https://www.myswitzerland.com/en-ch/experiences/summer-autumn/listicles/the-magic-of-blossoms/
These are just some ideas. April can be very beautiful.