[switchman2210]

Why don’t you use Sigil to build a epub based book which you can then convert to Mobi. If you are starting from a different format, you could use calibre to generate the initial epub file which you could then edit in Sigil. I did this last week. I started with an old lit file I had, converted it to epub in caliber and then reformatted it in Sigil to clean up the conversion issues. In my case I left it as an epub file, but you could then convert it to mobi.