How to format the TOC with toc=flat, left (KOMA)

[ah]

Dear lyx-user,
in Koma-Script (4th ed.) I found the command 
"toc=flat, left" 
for a TOC in table-format (which means: without indent of section and
subsections; see as well jpg attached).
Inserting in preamble    toc=flat, left         there ist no effect. 
Inserting a same TeX-command in document (before the table of content) there
is no effect as well. 
How can I  achieve success?
Best 
Andreas