Yes, it is too old.
\raggedchapter
has been introduced early this year to give the user the possibility to change the appearance of chapter and sections individually. There is also
\raggedpart
by the way.
Have you tried the commented line in the code above? It should work for you just fine.
All the information on what your version of KOMA-script can do is written in the documentation. You can call it in the terminal by typing and hitting enter:
KOMA can do a lot more than the standard classes, hence the manual is quite big. You can search for the specific term of
raggedsection
, but i would suggest to skim the table of contents as well.
The smart way: Calm down and take a deep breath, read posts and provided links attentively, try to understand and ask if necessary.