You can assign a name to an element path to capture the element content in a DITA2Go user variable of that name.
To map an element path to a user variable:
[VariableMaps] ; element path = name to use for variable with element content ; default is the element name itself elementpath = varname
[VariableMaps] mainbooktitle/* = BookTitle
The user variable is then available for use in DITA2Go macros. This assignment applies to any element, regardless of the properties set for the element in [ElementTypes]. How many variables you get depends on how many instances of the element path occur in your document. For example, if you set:
[VariableMaps] title/* = MainTitle
you will get a variable $$MainTitle[index] for every use of title in your document. If you change the setting to:
[VariableMaps] title/map/1 = MainTitle
you will get just one variable, $$MainTitle. How specific you make the path determines how many matches you get.