This is another instance where I'm just doing it wrong, but noting as a possible  ...I don't know what the right word is - usability issue, maybe? UX?  Something along those lines.

Using:  GNU Emacs 31.0.50 (build 1, aarch64-apple-darwin23.6.0, NS appkit-2487.70 Version 14.7.5 (Build 23H527)) of 2025-05-13

GNU Hyperbole 9.0.2pre (downloaded today)

====

In this case, attempting to perform Koutliner actions while the *scratch* buffer is active:

a) M-x hyperbole, k, o =>

Debugger entered--Lisp error: (error "(kotl-mode:is-p): ’*scratch*’ is not a valid Hyperbole koutline")
        error("(kotl-mode:is-p): '*scratch*' is not a valid Hyperbole koutline")
        hypb:error("(kotl-mode:is-p): '%s' is not a valid Hyperbole koutline" #<buffer *scratch*>)
        kotl-mode:is-p()
        kotl-mode:show-all()
        kotl-mode:overview(nil)
        funcall-interactively(kotl-mode:overview nil)
        hui:menu-act(hyperbole nil nil nil)
        hyperbole(nil nil nil nil)
        funcall-interactively(hyperbole nil nil nil nil)
        command-execute(hyperbole record)
        execute-extended-command(nil "hyperbole" "hyperbole")
        funcall-interactively(execute-extended-command nil "hyperbole" "hyperbole")
        command-execute(execute-extended-command)

However,

b) C-h h, k, o =>

reports  "hypb:error: (kotl-mode:is-p): ’*scratch*’ is not a valid Hyperbole koutline" in echo.

At the point I got these messages I was following along with the Info manual (2.1 Invocation) and just randomly selected K , O to see what it did.    I hadn't yet read the bit about o(vervw) "Show[ing] first line of each cell", (9.1 Koutliner Menu Commands) so fair enough,  I tried to perform an illegal action (attempted that action in a non-Koutliner buffer). 

Further confusion was had when I ran the commands in a .kotl buffer and it (appropriately, although I didn't realize it at the time) showed me the first line of each cell.   I assumed most of my existing text had been deleted, so I tried a C-/ to undo. 

That sent a rather inscrutable "Changes to be undone are outside visible portion of buffer" message.   That error seems to be caused by attempting to undo a narrowed region.  Which, unbeknownst to me, was turned on.  (Clear as day, there was 'Narrow' in my mode-line.) So I followed the advice in the linked thread and invoked M-x widen.

Great, everything returned!  (I eventually figured out that C-h h k a would do it too).   But M-x widen also inserted this at the bottom of my .kotl buffer:

"ben" ;; kvspec:current
1 ;; id-counter
alpha ;; label-type
4 ;; label-min-width
". " ;; label-separator
3 ;; level-indent

;; depth-first kcell attributes
[[0
  (creator "cena@byzantium" create-time "20250514:19:33:49" id-counter 1)]
 [1
  (creator "cena@byzantium" create-time "20250514:19:33:49")]]

(C-h h k a did not insert the above). 

I ASSume it's something to do with the cell properties, but I didn't make any changes there - this is all from a fresh install and just typing in a .kotl file using whatever the default settings are, then running commands.

Best,

Cena Mayo