It seems to me that it is not possible to create a ToC starting from level 3 (sub chapter). The feature is currently limited to level 1 (Entire document) or level 2 (Chapter) in the Edit Index > Type > Create ToC for… contextual menu of the table of contents.
Anyway I submitted the following request for enhancement:
https://bugs.documentfoundation.org/show_bug.cgi?id=130318
Does anybody have an idea to circumvent this limitation in the meantime?
I attach an example file of what I mean.
Apart from manual editing the “partial” TOCs (right-click and Edit Index, uncheck Protected against manual changes, then deleting the offending parts), I don’t see an automatic solution presently. If you have many such TOCs, it becomes quickly tedious and impractical.
I have many of them. I am currently updating them one by one… You are right, very impractical.
Edit Index (right click on TOC)
Ignore the box that says “For:” to the right there is another box that asks you to choose a level. Use that one.
No, this setting will limit the maximum level but does nothing on the minimum level.
The point in the original question is to collect only the elements (headings) relative only to the heading subtree of the present location. The current TOC engine collects everything, without consideration of the location of the TOC in the logical structure of the document.