I am running GNU Emacs 27.1 build as x86_64-pc-linux-gnu with GTK+ Version 3.22.30
and cairo version 1.15.10.

I have a texinfo file (test.texi attached) where I defined some additional sectioning
commands (e.g. @usec, @usebsec).  I customarily switch on outline-minor-mode to see the
headings.  outline-minor-mode gives the possibility to define my own set of headings
(e.g. @usec, @usebsec) by setting up "outline-heading-alist".  

With the default settings I get  


@node uchapter-amcoh
@unnumbered 6 @ Ameliorating Waveform Coherency...

Have modified my init file with the following code that resets "outline-heading-alist"
to include @usec, @usebsec as headings in addition to @unnumbered

(defvar texinfo-hdlevels
      '( ("@chapter" . 2)
	 ("@section" . 3)
	 ("@subsection" . 4)
	 ("@subsubsection" . 5)
	 ;; --------------------------------------------------
         ("@unnumbered" . 2)
         ("@unnumberedsec" . 3)
	 ("@unnumberedsubsec" . 4)
	 ("@unnumberedsubsubsec" . 5)
         ;; --------------------------------------------------
         ("@appendix" . 2)
 	 ("@appendixsec" . 3)
         ("@appendixsubsec" . 4)
	 ("@appendixsubsubsec" . 5)
         ;; --------------------------------------------------
	 ("@majorheading" 2)
         ;; --------------------------------------------------
	 ("@chapheading" 2)
	 ("@heading" 3)
	 ("@subheading" 4)
	 ("@subsubheading" 5)
         ;; --------------------------------------------------
	 ("@uchap" . 2)
	 ("@usec" . 2)
	 ("@usubsec" . 3)
	 ("@usubsubsec" . 4) ))

(setq-local outline-heading-alist texinfo-hdlevels)

I was expecting to see the following

@node uchapter-amcoh
@unnumbered 6 @ Ameliorating Waveform Coherency
@usec @value{seclb} Abductive Reasoning...
@usec @value{seclb} Parsimony over Complexity...
@usubsec @value{seclb} The Claerbout Conjecture...
@usec @value{seclb} Correlograms in Helioseismology...
@usubsec @value{seclb} Solar Magnetic Cycle and the Interface Dynamo...

But I am only seeing 

@node uchapter-amcoh
@unnumbered 6 @ Ameliorating Waveform Coherency...

> 
> I have a variable ‘texinfo-section-list’ whose value is:

---------------------
Christopher Dimech
General Administrator - Naiad Informatics - GNU Project (Geocomputation)
- Geophysical Simulation
- Geological Subsurface Mapping
- Disaster Preparedness and Mitigation
- Natural Resource Exploration and Production
- Free Software Advocacy


> Sent: Thursday, May 13, 2021 at 2:35 AM
> From: "Yuri Khan" <yuri.v.khan@gmail.com>
> To: "Christopher Dimech" <dimech@gmx.com>
> Cc: "help-gnu-emacs" <help-gnu-emacs@gnu.org>
> Subject: Re: outline-heading-alist for elisp using ";; * "
>
> On Wed, 12 May 2021 at 19:43, Christopher Dimech <dimech@gmx.com> wrote:
> 
> > Some have been trying to set outline-heading-alist fol/lowing the code in "texinfo.el".
> > I have also tried to set it up but have not been successful.
> 
> There is a group of people on this list, including you,
> michael-franzese, pietru, steve-humphreys, and wael-zwaiter, who seem
> to be working on a common project, have various difficulties, and post
> requests for assistance that are hard to follow through.
> 
> You state an approach (“I have tried this…”), followed by something
> general like “I have not been successful” or “I encountered
> difficulties” or “I need assistance”, but it is not readily clear how
> to assist you. So you get unhelpful answers or no answers at all.
> 
> The standard assistance request form includes:
> 
> * Your software version(s) and operating system (if you feel it might
> be relevant). This is important because if you are using older
> software, you won’t be able to use some solutions, or people will say
> it just works on newer versions.
> * What high-level problem you are trying to solve. This is important
> because sometimes people will say your approach is wrong and point you
> at a better way to solve it.
> * How you are trying to solve it.
> * What concrete result you expected.
> * What concrete result you observe instead.
> 
> Your above request could look like:
> 
> ===
> I am on GNU/Linux, running Emacs 27.1.
> 
> I have a variable ‘texinfo-section-list’ whose value is:
> 
>     ((chapter 2) (section 3) (subsection 4) (subsubsection 5)
>      (unnumbered 2) (unnumberedsec 3) (unnumberedsubsec 4)
> (unnumberedsubsubsec 5)
>      (mychapter 2) (mysection 3) (mysubsection 4))
> 
> (note my custom section macros).
> 
> I want to set up Emacs so that, when I open a texinfo file,
> outline-minor-mode is enabled and configured to recognize section
> macros listed in ‘texinfo-section-list’ as headings.
> 
> To that end, I’m trying this:
> 
>     (defun my-texinfo-outline ()
>       (setq-local outline-heading-alist
>         (mapcar (lambda (x) (cons (concat "@" (car x)) (cadr x)))
>                 texinfo-section-list))
>       (setq-local outline-regexp
>         (concat (regexp-opt (mapcar 'car outline-heading-alist) t)
>                 "\\>")))
> 
>     (add-hook 'texinfo-mode-hook #'my-texinfo-outline)
> 
> When I open the attached texinfo file, put point on line 42 and press
> C-c @ C-d (outline-hide-subtree), I expect the whole section up to
> line 68 to be hidden but not further lines, because line 69 has a
> custom section header; but Emacs hides everything up to line 86.
> ===
> 
> (and don’t forget to actually attach a sample file, as short as
> possible to demonstrate the problem).
>