This command is used as part of the Document per Repeated Item feature.
When a separate document is required for each of a set of repeating items, but only where certain criteria apply to the item, then the <<SetMultipleDocumentFilter>> command can be used to filter the repeating items so as to achieve this.
For example, suppose there is a repeating data element Child and a separate letter is required for each child, but only where the child’s age is greater than 12. The SetMultipleDocumentFilter command will then be:
<<SetMultipleDocumentFilter(Age > 12)>>
Note that the scope of the Age data element is actually Child.
In order to compare the child’s Age with a minimum age somewhere at the root level of the data set, the following would be used:
<<SetMultipleDocumentFilter(Age > ../MinimumAge)>>
The Cookbook recipe referred to above will have more discussion on this.