Kerbal Space Program

1) In the flight view, it's hard to know if the vessel markers (the purple rectangle overlays toggled by F4 key) are enabled, especially if you don't know where the marker is supposed to be in the first place.
My solution is to have an onscreen confirmation whenever the vessel marker overlay is enabled/disabled, just like for the aerodynamics and thermal overlays.

2) When a vessel is tracked, but its marker is off-screen (not in view of the camera), there should be an indicator on the edge of the screen pointing to the direction of the marker.
This makes it easier to find the target, which is small and otherwise hard to find.

The image below shows a concept of both of these UI elements in the flight view.