There is a way to do this in SmartView Tracker (the so-called "Active Connections" view).
While there is no shortcut to SmartView Tracker installed, you can find the binary in C:\Program Files (x86)\CheckPoint\SmartConsole\R80.10\PROGRAM as CPlgv.exe
And, as it turns out, this function still works (performance implications apply).
You can filter the results as desired.
You can also do this in SmartView Monitor to track this over time, if you enable Monitoring on the relevant Gateway object.
In R80+:
- Open SmartConsole > Logs & Monitor.
- Open the catalog (new tab).
- Click Tunnel & User Monitoring.
See also: Logging and Monitoring R80.10 (Part of Check Point Infinity)