I have a document like this:

    \starttext
        \index{dogs}
        
        \index{cats}
        
        \index{flowers}
        
        \index{snails}
        
        \index{trees}
        
        \placeindex
        
    \stoptext
    
As I understand, if you use \index{animals+dogs}, it will place dogs as a sub-category of dogs.

Is there any way to control this centrally, for instance:

\addtosub[animals]{dogs, cats, snails}
\addtosub[plants]{flowers, trees}

Such a way would make it so \index{dogs} places an entry for "dog" under "d" and "animals --> dogs" under "a".

--Joel