Track the fundraiser who interacted with a donor without using the Created By field on interactions

If i want to do a bulk import of interactions for multiple members of my team, I want to properly credit each team member. I can only do that if I can include the created by tag.

For example: Several people in our organization sent 50 Christmas cards each from custom lists. They were all hand written. If they had to also create an interaction for each, it would create a huge amount of manual work. If I could do a bulk import, with a created by field, the innteractions could be properly noted.