\startmode[ebook]
\setupbackend[export=yes]
\stopmode

\starttext

\index{Knuth}\input knuth

\index{Ward}\input ward

\index{Zapf}\input zapf

\startnotmode[*export]
\completeregister[index]
\stopnotmode

\stoptext

Unfortunately, this does not suppress generation of index references in the exported output. Here is a snippet of the -div.html file generated by the example you provided:

<div class="registerlocation index" href="#aut-1" onclick="location.href=&apos;#aut-1&apos;"><!--empty--></div>Thus, I came to the conclusion that the designer of a new system must not only be the implementer and first large--scale user; the designer should also write the first user manual.

Thus the request for a (simple) mechanism to redefine or disable standard commands. There are commands other than \index that might also benefit from similar treatment.

--
Rik