MobileRead Forums - Ho do I create a TOC for ePub which does convert to an active TOC in Kindle Previewer

Since Amazon hast decided to go KindleGen 2.x in October, calibre cannot be used anymore for creating valid Mobi files (at least not valid for KDP, they should still work when uploaded via USB).

Amazon's realm of oblivion (or PITA) is its "active TOC".

When I take an ePub file created in calibre (valid, and working absolutely fine) and use the Kindle Previewer to convert it to Mobi, the TOC icon is greyed out. When I upload the file to my Kindle 4, I cannot choose "Goto > TOC" from the menu, also greyed out.
NCX is working fine, though.

So: how may I create a TOC in calibre for my ePub file which will convert to an active TOC for Mobi on the Kindle Previewer.

I also tried Sigil and let it create the TOC on a calibre ePub. Didn't work, either.

Any help is very much appreciated! The countdown is one week and ticking.