Currently split-tunneling only allows applications to bypass the VPN and go straight to the ISP.
However, my situation has to do with being able to reach local/LAN IP-addresses/servers.
With the option "Only use PureVPN DNS when connected" (in Advanced Options --> Security) switched ON, I'm having difficulty reaching internal servers based on DNS-names. This is logical since the DNS-request doesn't reach the internal DNS-server. Of course, I can switch off this feature but then I don't have control on which DNS request are going to the ISP.

If I'm able to add the internal IP-range to the split tunnel I can lead all internal traffic to bypass the VPN tunnel and thus reach the internal (DNS- and other) servers.