The Supernovae page allows you to decide if the supernovae are displayed or not by checking the Show supernovae checkbox. By default, supernovae are drawn as small light orange “+” mark. As for satellites, the color of supernovae can be easily customized using the Colors page.
You can configure KStars to check for newly discovered supernovae on startup by checking the Check for Recent Supernovae on Startup checkbox. This way, KStars will be always up-to-date with the most recent supernovae. You can enable supernova alerts using the Enable Supernova alerts checkbox. Thus, KStars will automatically alert you every time it learns of a new supernova in the sky. You can set the magnitude limit for showing a supernova as well as magnitude limit for supernova alerts using the spin boxes control. The limiting magnitude is the faintest apparent magnitude of an skyobject that is visible with the naked-eye or a telescope.
The list of recent supernovae can be updated via the internet by pressing the Update List of Recent Supernovae button. Another way for updating the supernovae list is to use the Updates → Update Recent Supernovae data item in the Data menu.