I had an icon at the bottom of the screen (kitty?) for adding and removing programs.
This square space inside the panel is called System Tray.
This has suddenly disappeared.
This means that the Package Manger was closed in a non-regular way last time.
How can I get it back?
Get the kitty back by simply starting Package Manager from KDE Menu (in System).
And check whether there is a mark at Package Manager > Settings > Configure Package Manager > General Settings > Enable system tray icon.
As you had the kitty before there should already be mark there.
If you did a fresh install chances are that you have ran in to a bug that has been fixed,
This bug can only be solved with the command shown [here]