PCE Emacs and outline_mode

I am trying to figure out how outline_mode works with PCE Emacs. Currently
this line

declare_emacs_mode(outline, library('emacs/outline_mode')).

is commented out so I do it manually in the console. I was then able to
select the outline mode. I also made sure that I set the outline_regex_list
correctly by manually sending the regex defined in prolog_mode to the
emacs_outline_mode object of interest. I can see (using find_fragment) that
there are fragments with style set to outline_hidden so that appears to
work. But there is no actual hiding. I tried send(Emacs_Editor, style,
outline_hidden, style(hidden := true)), where Emacs_Editor is the editor of
interest, but that does not seem to change anything.

Is hidden text supported? The reference manual seems to say yes. How can I
activate it?

Is there a concept of minor mode a la emacs in PCE Emacs? I am wondering
how one can get outline_mode to work together with the prolog_mode.

Thanks for any help.
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