visibility of the subtree at that level.
If equal to a lambda function or function name, this function is
-expected to toggle headings visibility, and will be
-called without arguments after the mode is enabled."
+expected to toggle headings visibility, and will be called
+without arguments after the mode is enabled. Heading visibility
+can be changed with functions such as `outline-show-subtree',
+`outline-show-entry', `outline-hide-entry' etc."
:version "29.1"
:type '(choice (const :tag "Disabled" nil)
(const :tag "Show all" outline-show-all)