--- a/.emacs-my	Sun Mar 03 14:19:08 2019 +0200
+++ b/.emacs-my	Mon Mar 11 12:19:49 2019 +0200
@@ -3523,7 +3523,8 @@
 (my--eval-after-load nxml-mode
   (if (<= emacs-major-version 25)
       (define-key nxml-mode-map [C-return] 'nxml-complete)
-    (define-key nxml-mode-map [C-return] 'completion-at-point)))
+    (define-key nxml-mode-map [C-return] 'completion-at-point))
+  (define-key nxml-mode-map [S-tab] 'hs-toggle-hiding))
 
 (defun my-nxml-pp ()
   "Pretty-print XML."