2) another macro should build an index at the end of the document. I use Lua to keep a list of all database tables referenced within the document (together with some metadata) and save it in the jobpasses struct. Now I also want to track the chapters, sections, etc where these references are, to be able to see, where a database table is used.

To solve these two problems, I'm looking for information about the current heading. The level and the associated reference name.
If I have the level, I can keep my own list of necessary heading types (subject, subsubject, ...) and just get the one at level+1 to write the heading using lua (tex.sprint(....)).
With the reference name I can obviously solve 2), since I then can simply keep a list for each db table in the jobpasses structure.