Orgmode plain list bullet : change automatically with list depth

[DEBRY . Edouard]

When making a plain list in orgmode, I would like to change of bullet
autmatically depending on the list depth.

Currently, I use this to prettify bullets :

(font-lock-add-keywords 'org-mode
                        '(("^ *\\([-]\\) "
                           (0 (prog1
                                  ()
                                (setq bullet "•")
                                (compose-region (match-beginning 1) (match-end 
1) bullet))))))

I attempted to this :
(font-lock-add-keywords 'org-mode
                         '(("^ *\\([-]\\) "
                            (0 (let* ((depth (org-list--depth 
(org-element-at-point)))
                                      (bullet (cond ((= depth 1) "•")
                                                    ((= depth 2) "▸")
                                                    (t "-"))))
                                 (prog1 () (compose-region (match-beginning 1) 
(match-end 1) bullet)))))))

for the bullet to change with respect to the org list depth, so to have
(e.g.) :
• test
  ▸ test1
  ▸ test2

But it breaks the org file.

How could I achieve this ?

Regards

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