scrreprt - add levels below \subparagraph

Quoting the manual from the titlesec package:

With the help of classes you may insert, say, a new subchapter level between chapter and section, or creating a scheme of your own.

(at subsection 3.9 in the titlesec.pdf).

At appendix 9.2, it shows exactly how the already existing sections and the like are defined; don't copy the already existing parts to your file, but use them as inspiration for defining new ones (amount of indentation, style, etc). My advice is to look at all the appendices and subsection 3.9.

Since the question is about a KOMA-class, we can use KOMA features to define new levels of structuring commands.

\documentclass{scrartcl}
\makeatletter
\DeclareSectionCommand[%
  tocindent=9.0em,%
  ]{subparagraph}
\DeclareSectionCommand[%
  style=section,%
  level=6,%
  indent=2.0\scr@parindent,%
  beforeskip=3.25ex \@plus1ex \@minus.2ex,%
  afterskip=-1em,%
  tocstyle=subsection,%
  tocindent=10.0em,%
  tocnumwidth=4.1em%
  ,font=\normalcolor\normalsize\bfseries\sffamily,%
]{Aparagraph}
\DeclareSectionCommand[%
  style=section,%
  level=7,%
  indent=3.0\scr@parindent,%
  beforeskip=3.25ex \@plus1ex \@minus.2ex,%
  afterskip=-1em,%
  tocstyle=subsection,%
  tocindent=11.0em,%
  tocnumwidth=4.1em%
  ,font=\normalcolor\normalsize\bfseries\sffamily,%
]{Bparagraph}
\DeclareSectionCommand[%
  style=section,%
  level=8,%
  indent=4.0\scr@parindent,%
  beforeskip=3.25ex \@plus1ex \@minus.2ex,%
  afterskip=-1em,%
  tocstyle=subsection,%
  tocindent=12.0em,%
  tocnumwidth=4.1em%
  ,font=\normalcolor\normalsize\bfseries\sffamily,%
]{Cparagraph}
\makeatother
\setcounter{tocdepth}{7}
\begin{document}
\tableofcontents
\section{Wombat}
\subsection{Capybara}
\subsubsection{Mara}
\paragraph{Zebra}
\subparagraph{Elephant}
\Aparagraph{Giraffe}
\Bparagraph{Quail}
\Cparagraph{Duck}
\end{document}

Of course you don't really need \makeatletter and \makeitother if you don't use low level commands. I used them, because i copied the bits straight from the class file.