Mapping an optional field to its optional subscript node

Hello all,

If we have a global structured something like this:-

1. ^test(1)="Dave^Engineer"
2. ^test(2)="Bethan^Manager"
3. ^test(2,"transferred")="2024-01-04"
4. ^test(3)="James^Administrator"
5. ^test(4)="Sophia^Marketing Executive"
6. ^test(4,"transferred")="2023-11-20"

It is fairly straightforward to map, and from a reading perspective everything works fine, but when inserting/saving the "transferred" node is created even if the 'transferred' field is not set. Is there a way to populate the node only if the field mapped to it is set?

Thanks

Colin