[divingbluefrog]

Yes I do. And I'm almost sure now that it's done via the text entry :
when a clickable zone, or a button is referenced with a text=x line in the Page file,
and it's displayed as string : [x]UPPERCASE in the Item Text zone (last one) of
the menu Editor, it's in fact a call to the Page xyz.ini file.
I think that the link between UPPERCASE name and xyz name is harcoded somewhere, cause I can't find a file giving it.

But there is another feature that bothers me now (I know, the more you learn, the more you discover the extent of your ignorance).
Let me prepare a clear explanation and I will post it soon.