Demo theme switcher

I don’t have a definitive answer, but can suggest investigating the plugins listed at https://www.ads-software.com/extend/plugins/tags/theme-switcher which may be worth investigating

for example this one https://www.ads-software.com/extend/plugins/wordpress-theme-demo-bar/screenshots/

I was looking for the same thing. So far, this is the closest I have found. You can edit the CSS, icons, etc. to make it look similar. Easy install – read through a few pages of the thread at least to make sure you understand what you need to change.

https://themeforest.net/forums/thread/introducing-item-switcher/42612?page=1

Searching on google I found this: Demo Switcher by Halil Kilic (https://www.sendspace.com/file/jp7xhe) is from tutspress.com but this site is closed and I can’t find a tutorial for installation