@JimLL
Everything you do has some Jargon and skills needed attached.
Ride a bicycle: Kick-stand, Handlebar, Shifter, De-railer....
Common instructions do not include how to manufacture or Modify that bicycle.
Same goes for Calibre.
Calibre (conversion) is a Modification tool. You are expected to know a bit about the e-book (input format) before you can do a
custom job on it (to get a different format).
As @advantman said: the default settings are usually good (for a typical, well formed source) . The computer adage GIGO still applies
The defaults expect certain Words to be used to detect section divisions: Chapter, Part, Epilogue...
If you book designer got
creative, you need to help things along.
Ex. Chapters that ONLY have roman numerals
Chapters with sub-titles (Calibre will usually break (leave) these apart)
Personally, I skip trying to craft additional auto-detect rules and simply spend some time
touching up with Sigil.
There, you can visually identify the desired TOC items and mark them (Sigil uses Heading levels to indicate TOC nest levels).
And Sigil generates the TOC from that at a click of a mouse.
An otherwise 'clean' EPUB takes me less than 5 minutes to polish the TOC (I do resort to using REGEX if I can)
Can you build a complete house? Did not think so
A Book is a House. The words on a page are just materials. The Author selects the words, the book layout designer is the Architect.
You simply need to take time and learn how to use your new power tools
before you start your remodel project