I have imported QIF bank files for a number of accounts and the accounts have transfers between the accounts. What is the correct way to process them so that there is a single transaction between the two accounts?

I thought that I would have had an answer by now. Is this question unclear or is it a complicated process?

Simply put - you don't.

Delete one transaction from each account so effectively the best you can achieve is to match one of the original bank files (if you are very careful).