Problem with Navigator.

There are 24 ‘Headings’ in a document. None of them appear in Navigator under Headings.
Watched a few YouTube videos regarding Navigator, none helped.

When creating a ‘Heading’, I use Styles, Heading.
System is Ubuntu 18.04 LTS, Libre Office version: 6.3.4.2.0+

Jules applies for a job in a deli.
Jules, 22, applies for work in a deli with Natalia and Renaud, the owners.
Jules is walking past a deli when she sees a ‘Help Wanted’ poster in the window. Jules enters the deli, approaches the counter where a woman waited with a nice smile and a the name Natalia hand written on an adhesive label.
Natalia
May I help you?
Jules
Yes, I hope so. My name is Jules, I am inquiring about the ‘Help Wanted’ sign.

How is this solved?

Could you upload an anonymized sample file showing the problem? Please add also some information about your operating system and the LibreOffice version you are using?

Please do not use Add Answer but edit your original question to enhance the details of your question. Thanks in advance …

Just installed 6.3.4.2 on an Ubuntu 18.04 test system and got no problem with visibility in Navigator. Did you already try to test whether your user profile could be the cause of the issue by using Safe Mode?

Test user profile causing issue:

  • Start in Safe Mode using Help -> Restart in Safe Mode and confirm the restart using button: Restart
  • Archive your profile expanding Advanced (click on the word Advanced right above Help button) and click Archive User Profile button
  • Click button Continue in Safe Mode
  • Open a file and test whether the problem is gone

If it works in Safe Mode most probably your user profile is corrupt and you should reset.

SOLVED
Thanks for the help.

Please use the comments, And would be nice to know the solution so other people can find it.