Select an option in the "Navigate by" widget in the Navigator panel and press F1. This opens  at the top of the page.
Enhancement: Open the page with "Navigate by" visible (because there is a lot of information on this help page, and not clear what to look for).
Reproduced with gen VCL in:
Version: 220.127.116.11 / LibreOffice Community
Build ID: f6099ecf3d29644b5008cc8f48f42f4a40986e4c
CPU threads: 8; OS: Linux 5.15; UI render: default; VCL: x11
Locale: en-AU (en_AU.UTF-8); UI: en-US
Dropdown was made available in 7.0, but "Navigate by" heading first appeared in the 7.1 documentation.
Rafael Lima committed a patch related to this issue.
It has been pushed to "master":
tdf#155884 Fix "Navigate By" target in help