Create a table of content (TOC)

[connium]

Is your feature request related to a problem? Please describe.
On a text document it should be possible to add/create a table of content (TOC).

Describe the solution you'd like
When adding a TOC, entries for all headlines in the document should be added with the appropriate level.
I suppose it won't be possible to set proper page numbers because that needs layout information.

Additional context
TBD Add any other context or screenshots about the feature request here.