Full syntax :
    #Subpage name
    
When you click on an link of the form <text=>.xxx> (Note the dot), then StrongHelp expects to find the new page in the current file. It searches for a line beginning with "#Subpage xxx", and uses the text from the line after and to the next #Subpage or end of file, as source for the new page.

Example:
Mainpage
This is a tiny page with a tiny <subpage=>.sub>
#Subpage sub
This is the tiny subpage.