Please consider implementing Safari-like gestures, e.g.:
“swipe back”: two finger swipe left-to-right
“swipe forward”: two finger swipe right-to-left
“zoom”: two finger pinch
“smart zoom”: double tap
My general suggestion would also be to consider some kind of deeper integration with Safari (since it is a Mac native browser) like access to passwords via iCloud Keychain (since 3rd party password managers do not seem to support DevonAgent).