I've been playing with outline-mode for the first time in a while. I've 
got a
simple suggestion: it seems like the `outline-blank-line' variable ought 
to be
customizable and file-local safe. It causes a single blank line to 
separate
hidden heading lines when there is at least one blank line in the 
un-hidden
text.

If you leave blank lines before some headings and not others, it 
provides an
additional visual way of grouping them, without the need to create 
another
heading level. This is handy if the distinction is temporary, as in: 
"I'm done
with these sections, but still working on those."

A trivial patch is below (and also attached). Version 22.1 is a guess on 
my
part, someone with better git skills than me could probably check it.

Thanks!
-Jeff

============================================================
--- outline.el.orig    2022-02-21 12:08:50.124838087 -0600
+++ outline.el    2022-02-21 13:05:59.087075549 -0600
@@ -294,8 +294,11 @@
  (defvar outline-mode-hook nil
    "This hook is run when outline mode starts.")

-(defvar outline-blank-line nil
-  "Non-nil means to leave unhidden blank line before heading.")
+(defcustom outline-blank-line nil
+  "Non-nil means to leave an unhidden blank line before headings."
+  :type 'boolean
+  :version "22.1")
+;;;###autoload(put 'outline-blank-line 'safe-local-variable 'booleanp)

  ;;;###autoload
  (define-derived-mode outline-mode text-mode "Outline"
============================================================