This feature in Stellarium is very helpful, would be cool to get it in KStars as well!
Oh, I found it in the docs! Quote: "You can add new satellites to KStars default satellites set by editing the kstars/data/satellites.dat file. As each line of this file is a group of satellites, you need to add a new entry for your desired satellites group. An entry should have the following format: Group Name;local_filename;url. For example: Iridium;iridium.tle;http://celestrak.com/NORAD/elements/iridium.txt." Tested it - works as expected. But the path was without the data subfolder (caused by difference between kstars and kstars-bleeding packages maybe?) You can close this ticket probably, though might be worth to leave it and maybe think about implementing it in UI, like in Stellarium.