Phew..! Took a while. 

Thank you for your endless patience and guidance! 

On Sat, 13 Apr 2024, 12:21 Eli Zaretskii, <eliz@gnu.org> wrote:
> From: Vladimir Kazanov <vekazanov@gmail.com>
> Date: Sat, 13 Apr 2024 10:32:01 +0100
> Cc: emacs-devel@gnu.org
>
> Sure, here's the code I used to test tooltips. Just eval the
> corresponding forms:
>
>   (insert (propertize "foo" 'left-fringe-help "left tooltip"))
>   (insert (propertize "foo" 'right-fringe-help "right tooltip"))
>
>   (overlay-put
>    (make-overlay (point) (1+ (point)))
>    'after-string
>    (propertize
>     "lll"
>     'left-fringe-help "left tooltip"))
>
>   (overlay-put
>    (make-overlay (point) (1+ (point)))
>    'after-string
>    (propertize
>     "rrr"
>     'right-fringe-help "right tooltip"))

Thanks, I've now installed the changes on the master branch.