[teutocat]

It seems that the "Any Screen Timeout Plus" app is ultimately just an alternative user interface for the hibernation timeout setting in the tablet's system settings. The tablet itself only allows 3, 5 or 10 minutes there, nothing else. If I select one of them and then start the "Any Screen Timeout Plus" app, this value is displayed as the default value in the app. But if I select e.g. 30 minutes or another value apart from 3, 5 or 10 in the app, "never" ("niemals") is displayed in the system settings, which could not even be selected there.
That leads me to the assumption that an app that wants a longer hibernation timeout doesn't have to use any special tricks at all, but simply does exactly what the system's Settings dialog does, only with more options.
The only small limitation is that a value other than 3, 5, 10 minutes is always reset to 5 minutes after restarting the tablet. A corresponding app would have to reset a special setting itself.