[NTG-context] Indexing redux

Hello experts, Is there a way to generate an entry without a page number in an register that has page numbers enabled? This would enabled /See also/ entries to be generated with something like \setregisterentry[TopicIndex][keys:2=zzz,entries:1=punctuation,entries:2={{\em See also} marking}]% I do see that there is an alternative key defined for the command, but no explanation of what the alternatives are and if any would help. -- Rik