You can just use your regular transaction entry screen. Choose either withdrawal or deposit, it doesn't matter because you're going to fill in the top half of the screen like normal, but leave the amount as $0.00 because in this transaction, no money went either in or out of your bank account.
Then you'll need 4 lines in the bottom half of the screen, three of type L-, to clear each of the three existing loans and then your last line can be L+ to record the new loan. Since line 1 + 2 + 3 is equal to line 4, you have a balanced transaction that you can record.
