You can use Kantu’s desktop automation feature to control any other proxy manager extensions (e. g. FoxyProxy, ProxySwitcher) or VPN extension (ZenMate, NordVPN,…) by sending hotkeys to the extension via XType or by actually automating the extension with XClick. This works already now.
As a future feature, we plan to add a built-in PROXY command to Kantu soon.