With that said, the scenario that you are trying to achieve is not currently possible with Shutter. Let's imagine we have two instances of Shutter, where instance A is configured to sleep after 30 mins and the instance B is configured to shutdown after 3 hours of inactivity. Once instance A enacts the sleep mode, instance B will be halted (like any other user space application) until the computer wakes up from sleep, so instance B will not be able to shutdown your computer after 3 hours of inactivity.
Your goal is better achieved with the standard power management features found in Windows. To adjust power and sleep settings in Windows 10, go to Start, and select Settings > System > Power & sleep.
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