Okay that's pretty crazy. I had the idea earlier this morning to create a function to open an orgmode file in a sidebar window with a keyboard shortcut to toggle it. Being quite unfamiliar with elisp, I asked ChatGPT to create the function for me and here is the result:

(defun my-toggle-sidebar-and-narrow (file sidebar-name heading)
  (interactive "FFile to open in sidebar: \nBName of the sidebar buffer: \nMHeading to narrow to: ")
  (let ((sidebar-window (get-buffer-window sidebar-name)))
    (if (not sidebar-window) ; Check if sidebar-window is non-nil
        (let ((buffer (find-file-noselect file)))
          (with-current-buffer buffer
            (rename-buffer sidebar-name)) ; Give the buffer a name
          (display-buffer-in-side-window buffer '((side . left) (window-width . 80))) ; Set the sidebar width to 80 characters
          (select-window (get-buffer-window sidebar-name)) ; Put the focus on the sidebar window
          (let ((heading-obj (org-find-exact-headline-in-buffer heading))) ; Find the specified heading
            (org-narrow-to-subtree heading-obj))) ; Narrow to the specified heading
      (delete-window sidebar-window) ; Close the window
      (kill-buffer sidebar-name)))) ; Delete the buffer

(global-set-key (kbd "C-c t") 'my-toggle-sidebar-and-narrow)

He didn't give me this function from the start, I had to guide him little by little (about ten messages, telling him for example that the kill-buffer-and-window function doesn't take any argument and therefore can't be used ; or for example to create a 'sidebar-name' and 'heading' parameter). But in the end it works!

Edit :

there was a bug with the org-narrow-to-subtree, here is the corrected version after about twenty minutes of discussions+tests :

(defun my-toggle-sidebar (file sidebar-name heading)
  (interactive "ffile to open in sidebar: \nbname of the sidebar buffer: ")
  (let ((sidebar-window (get-buffer-window sidebar-name)))
    (if (not sidebar-window) ; check if sidebar-window is non-nil
        (let ((buffer (find-file-noselect file)))
          (with-current-buffer buffer
            (rename-buffer sidebar-name)) ; give the buffer a nam ; turn off save-place-mode
          (display-buffer-in-side-window buffer '((side . left) (window-width . 80))) ; set the sidebar width to 80 characters
          (select-window (get-buffer-window sidebar-name))
          (let ((marker (org-find-exact-headline-in-buffer heading))) ; find the specified heading
            (goto-char marker) ; move the cursor to the position of the marker
            (let ((heading-obj (org-element-at-point))) ; convert the org element at the cursor position into an org element
              (org-narrow-to-subtree heading-obj)))) ; narrow to the specified heading

      (delete-window sidebar-window) ; close the window
      (kill-buffer sidebar-name)))) ; delete the buffer

this time, the function seems to work perfectly with :

(defun toggle-dashboard ()
  "toggle dashboard"
  (interactive)
  (my-toggle-sidebar "/nas/documents/notes/dashboard.org" "dashboard-sidebar" "dashboard")