. Some words have to be defined as Headings, to be included in a Table of Contents in a document prepared inLibre office writer software. What can be used for this

options are
a) Style b) Clone c) Filter d) Mail merge

No clear enough to be understood. Please edit your question to give a better description of your purpose and possibly an example (either of your attempted procedure or of the expected result).

By the way, try to have a short question title. The description is there for lengthy development.

Read these guidelines and ask a good question.

This (and the other Q by OP) look like a “test”. Just wondering who is the testee?