Index: import 'see' and 'see also' references from other document

I remade a new document from one that got corrupted.

All the index markers are, of course, in the text.

But the index also contains a lot of  'see' and 'see also' cross references (192 in all). These are evidently not stored in the text, but somewhere in the original document.

Is there any way to get these references into the new document? Importing topics from the original document doesn't do the trick: it imports the topic, but not the references, of course. 

So the cross-reference 'Absence see Judgment (default)' comes in as 'Absence' only, because that is the topic, the rest is the reference.

Can anyone suggest a solution other than having to insert them one by one?