I know how to enable\disable it per user:
You need to configure the Computer Configuration's Remote Desktop Session Host policies:
Launch the Global Policy Editor with typing gpedit.msc from the command-line and hit Enter.
In the left panel, navigate to Computer Configuration > Administrative Templates > Windows Components > Remote Desktop Services > Remote Desktop Session Host > Session Time Limits.
In the right panel, double-click the Set time limit for active but idle Remote Desktop Services sessions policy: in the modal window that will appear, activate it by switching the radio button from Not configured to Enabled, then set the desired amount of time in the drop-down list right below.
But what I am trying to do is find out if there is a setting to disable it por user or per user group?
At this point, I'll even accept tricks on how to bypass it. I've tried mouse movers, key presses, webpage reloads and it still knows I'm idle.