Handle sublists when sorting for original order.

Fixes alphapapa#207

org-super-agenda.el

@@ -836,7 +836,7 @@ The string should be the priority cookie letter, e.g. \"A\".")
                  for (auto-section-name non-matching matching) = (org-super-agenda--group-dispatch all-items filter)
 
                  do (when org-super-agenda-keep-order
-                      (setf matching (sort matching #'org-entries-lessp)))
+                      (setf matching (org-super-agenda--sort-matches-for-original-order matching)))
 
                  ;; Transformer
                  for transformer = (plist-get filter :transformer)
@@ -900,6 +900,31 @@ The string should be the priority cookie letter, e.g. \"A\".")
     ;; No super-filters; return list unmodified
     all-items))
 
+(defun org-super-agenda--sort-matches-for-original-order (matching)
+  "Sort MATCHING items back into their original ordering based on `org-entries-lessp'.
+Only used when `org-super-agenda-keep-order' is non-nil."
+  (--sort
+   ;; Sorting has a shallow element of recursion because not all of the given items
+   ;; are matched org headlines that can just be sorted using `org-entries-lessp'.
+   ;; Some super-agenda matchers, like `:auto-category', will introduce sublists
+   ;; whose contents need sorting of their own. In that case the lists' `:items'
+   ;; properties need to be sorted instead.
+   (let ((first-is-list (listp it))
+         (second-is-list (listp other)))
+     (when first-is-list
+       (plist-put
+        it :items
+        (sort (plist-get it :items) #'org-entries-lessp)))
+     (when second-is-list
+       (plist-put
+        other :items
+        (sort (plist-get other :items) #'org-entries-lessp)))
+     (cond
+      (second-is-list t)
+      (first-is-list nil)
+      (t (org-entries-lessp it other))))
+   matching))
+
 ;;;;; Auto-grouping
 
 (cl-defmacro org-super-agenda--def-auto-group (name docstring-ending