I have an AR750S, firmware 3.003. Under More Settings → Button Settings, I can set the “Switch Button” to a few things. I selected “OpenVPN Client Toggle (On/Off)”.
When toggle is in the ON position, the current configured OpenVPN Client should automatically connect. If connection fails for any reason, it should automatically reconnect.
When toggle is in the OFF position, OpenVPN should be disconnected if previously active.
Bonus behavior would be that the firewall rules are automatically adjusted to pass LAN traffic to the WAN either directly or via the VPN, depending on the switch state.
Regardless of switch state, I must manually navigate to the VPN → OpenVPN Client menu and click the connect button. Switching from ON to OFF does disconnect the VPN if already connected, but switching from OFF to ON does nothing. While switch is ON, if the VPN becomes disconnected, it does not automatically reconnect.