It is a PDF outline editor as an alternative to proprietary PDF editors.
I built it for myself to replace handyoutliner that I was not able to run it on macOS.
Export the table of content read from the PDF file
from outline import export_outline, import_outline
if __name__ == "__main__":
export_outline("target.pdf", "toc.txt", 13)Example of toc.txt (offset 13 has been applied except for the first entry)
You can skip offsetting page number with # symbol (#5)
Ch1. First Chapter at page 1 (1)
Define children with indentation of 4 spaces (5)
Or children of children (10)
Ch2. Something else at page 30 (30)
Import TOC from toc.txt and write to the PDF file
from outline import export_outline, import_outline
if __name__ == "__main__":
import_outline("target.pdf", "toc.txt", 13)