\setupregister[index][n=1]

\starttext

hello \index{aa}
hello \index{aa+aa}
hello \index{aa+bb}
hello \index{aa+cc}

hello \index{bb}
hello \index{bb+aa}
hello \index{bb+bb}
hello \index{bb+bb+aa}
hello \index{bb+bb+bb}
hello \index{bb+cc}

hello \index{bb}
hello \index{bb+aa}
hello \index{bb+bb}
hello \index{bb+bb+aa}
hello \index{bb+bb+bb}
hello \index{bb+cc}
hello \seeindex{bb+aa}{foo}
hello \seeindex{bb+bb}{foo}
hello \seeindex{bb+bb+aa}{foo}
hello \seeindex{bb+bb+bb}{foo}
hello \seeindex{bb+cc}{foo}

hello \index{cc}
hello \seeindex{cc+aa}{foo}
hello \seeindex{cc+bb}{foo}
hello \seeindex{cc+bb+aa}{foo}
hello \seeindex{cc+bb+bb}{foo}
hello \seeindex{cc+cc}{foo}

hello \index{dd}
hello \seeindex{dd}{foo}

hello \seeindex{ee}{foo}

\blank[3*big]

\placeindex[criterium=all]

\stoptext

