Adding code folding to syntax highlighting

Hi all,

I am trying to add code folding to the RSI IDL syntax highlighting [1], 
for multi-line loops

(syntax:

for XXXX do begin

   YYYY

endfor)

Following the documentation [2] and the example for a C source file [3], 
I have added the following lines to the "Normal" context in the xml file:

<StringDetect attribute="Keyword" context="#stay" String="begin" 
beginRegion="Control"/>
<StringDetect attribute="Keyword" context="#stay" String="endfor" 
endRegion="Control"/>
<StringDetect attribute="Keyword" context="#stay" String="endif" 
endRegion="Control"/>


But it doesn't work (no foldable sections are created in Kate).

Any ideas on what I'm doing wrong? (Kate 17.12.3, KDE Frameworks 5.44, 
Kubuntu 18.04.5).

Thanks a lot!

Enrico

[1] https://kate-editor.org/syntax/data/syntax/rsiidl.xml

[2] https://docs.kde.org/stable5/en/applications/katepart/highlight.html

[3] https://kate-editor.org/syntax/data/syntax/c.xml