The front-end-based local "Insert>Hyperlink… " works fine if the notebooks remain in their original folders. Moving them to another folder apparently breaks the local links because they use an absolute file-path.

The method with the inline Hyperlink-commands circumvents this by permitting to use a relative file-path. I didn't find an equivalent method using the front-end. Thus it may be possible to move a set of interlinked notebooks while conserving the functionality of the links.

Up to now I have used the following procedure – still wondering if there can be found an easier way:

Position insertion-line on link-place within the (text-) cell of the notebook.

Type ctrl-9 to produce inline cell.

Enter Hyperlink-expression into inline-cell:

Hyperlink["text to be shown",{"HyperlinkTarget.nb","targettag"}]

(be sure the inline cell content is selected) then menu-draw "Evaluation>Evaluate in place" or Ctrl+Shift+Return

The (text-)cell with the hyperlink text "text to be shown" should be working. (Mathematica 14.2)