(with-eval-after-load 'org
  (defun my-org-notmuch-search-store-link ()
    "Store a link to a Notmuch thread."
    (interactive)
    (require 'notmuch)
    (when (eq major-mode 'notmuch-search-mode)
      (org-store-link-props
       :type "notmuch"
       :link (concat "notmuch-search:" (notmuch-search-find-thread-id t))
       :description (notmuch-search-find-subject)))))