DyalogHelpDir

This parameter specifies identifies the location of the HTML-based help that is used for a request for help (from the Help menu or pressing F1) from the Session. It may be:

• The full pathname of the directory that contains the Dyalog APL help file (dyalog.chm). This is the default.
• The index page of the on-line HTML-based help located on help.dyalog.com for example, https://help.dyalog.com/18.0.