Is there an app to toggle proxy settings on non-rooted Android phones?
require root for some reason


It requires root because the global proxy setting is a secure system settings; on nonrooted devices, only system apps (like the Settings app) can modify secure system settings. Imagine if just any app can modify your global proxy setting, you can inadvertantly be redirecting all your internet traffics to some shady server somewhere across the globe.

Your alternative is to set up two browsers, one that uses normal internet and another that than can have per-app proxy configuration. You can set Firefox for Android to use a proxy by changing the network.proxy.http and network.proxy.http_port setting from within about:config. More details: https://support.mozilla.org/en-US/questions/757976.