I think something like the following will do (untested):
(defun org-attach-save-file-list-to-property ()
"Save list of attachments to ORG_ATTACH_FILES property."
(when-let* ((dir (org-attach-dir))
(files (org-attach-file-list dir)))
(org-set-property "ORG_ATTACH_FILES" (mapconcat #'identity files ", "))))
(add-hook 'org-attach-after-change-hook #'org-attach-save-file-list-to-property)Best, Ihor
