There are several authorization methods that you can find in this subsection.
The user is automatically logged out when inactive (no internet connections) for 15 minutes (except connections via VPN).
Keep in mind, that the operating system itself can also generate traffic (for example Windows telemetry) without user intervention. Because of this, the timeout for the user will be constantly reset and will not be able to function correctly.
For the new timeout to be applied, you need to reboot SafeUTM.