A powerful, yet underestimated, feature of Writer is the “Navigator” (
F5 if not yet displayed in the side pane).
The Headings section exhibits the chapter structure of your document shrinkable tree. Double click on any chapter title to jump there. TOC is one the “chapters”.
CAUTION! this relies on a consistent use of the Heading n paragraph styles.
Edit (use the edit link) your question to describe what you mean with “floating hyperlink” in terms of visual aspect and behaviour; what is the target of the link? is it included in some paragraph of the main text flow? Is it set on its own on the side of the text (like a picture)? Any information useful to imagine an implementation. I’ll then update my answer.
To show the community your question has been answered, click the ✓ next to the correct answer, and “upvote” by clicking on the ^ arrow of any helpful answers. These are the mechanisms for communicating the quality of the Q&A on this site. Thanks!