Do there exist command line options to install and make active: colorthemes, windowborders, plasma-themes and icon-themes? I can't find documentation regarding these items.

That would be practical because I could make a script execute these tasks.
Thanks.

In this case, you are probably best to refer to the KDE Source Code for this. You will likely need to use qdbus combined with kwriteconfig to change these settings and inform applications of the change.

Thank you for pointing me into a possible direction. So I see: there is no easy way. Now I can start looking!