Hi Hitch,
thank you for your answer. I took a few screen shots while importing the HTML file shown above and generating the table of contents:
The first step was a import from a HTML file:
The second screen shot shows the project in MobiCreator after the import:
The third screen shot shows, how I started to generate the table of contents:
Here are my settings for the generation:
And finally the error message I got after pressing the update button:
