I was using this tool at some point in the past.
Right now I cannot locate it.
One click VPN connection aimed at less-technical users using WiFi from libraries and coffee-shops...
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I think you are talking about tunnelblick.
This is what I am using, and it is indeed a one click that sits in the tray after setup.
For OpenVPN all you need is the .ovpn file.
here is the link: https://tunnelblick.net/
Could it be you are talking about Cisco AnyConnect Secure Mobility Client? Here is what it looks like just after I launch it, you input the server address and your credentials and that's really all it needs!
TunnelBear is one, but with its cutesy animations, you'd be likely to remember using it. https://www.tunnelbear.com/