This document outlines functionality, user interface design and considerations for improvements of screen management in Plasma.
Here are some examples of what kind of scenarios kscreen serves.
The user has a more or less static setup, for example two monitors next to each other on a desktop computer.
After installation, the user has to set the relative position of the displays, so the mouse cursor leaves one and enters another output on the physically adjacent edges. Ideally, he does this once, from then on, settings are stored and adjusted on login.
A laptop that is sometimes connected to a docking station with additional monitors connected.
Docking stations are basically multiple connections in one. Docking station-connected monitors are essentially the same as directly connected monitors, through HDMI, VGA, etc.. They're usually identified as DisplayPort connections. An interesting detail about docked monitors is that they might not show up until connected, so they might be either displayed, but disconnected (and thus not enabled), connected and enabled, or not present at all. Not displaying disconnected displays in the UI of course solved this dichotomy, at the technical level, it's handled correctly.
Kscreen restores previously saved settings when this docking station (and monitor) is connected. The use may close the lid of the laptop, in that case, all screen contents moves to the external monitor. (There's a setting to suspend the machine regardless, in that case, screen content isn't changed. Output connections are reconsidered post-resume and restored.
A projector is connected to a laptop to hold a presentation.