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Tables in two columns.

\Configure{theindex} 
   {\Columns[WIDTH="100\%",VALIGN="TOP"]{2}} {\EndColumns} 
   {\idx:tbl}  {\endidx:tbl} 
   {\idx:tbl\idx:sub}  {\endidx:tbl} 
   {\idx:tbl\idx:sub\idx:sub}  {\endidx:tbl} 
   {\hbox{\HCode{<P>}}} 
\def\idx:tbl{\hbox\bgroup\HCode{<TABLE \:zbsp{theindex}><TR 
   CLASS="theindex"><TD CLASS="theindex">}} 
\def\endidx:tbl{\HCode{</TD></TR></TABLE>}\egroup} 
\def\idx:sub{\ \HCode{</TD><TD CLASS="theindexsub">}} 

Redifine \index and \glossary to add the ‘\beforeentry{file name}{tag}’ before each \indexentry and each \glossaryentry, with default definition for \beforeentry to eat its fields and do nothing.

In addition, The command inserts a tag at the file. To get a pointer to the file, all we need to insert te redefinition ‘\def\beforeentry#1#2#3#4{#3{\Link[#1]{#2}{}#4\EndLink}}’ which puts the link on the page number (for whatever the page number is good, or replaces it with another mark).