I frequently need to be able to record a transaction at three different accounts, in sequence. Examples (we are a non-profit org):

Contribution from John Jones -to- John Jones account -to- Deposit #---.

Purchase on debit card -from- debit card account -from- checking account

In the Jones example, it is necessary to have a record of Jones' donations for annual tax-time receipts, but these should not be part of the Checking Acct. total. The donation amount should add to the Deposit.  At present, I seem to have to go directly from John Jones Account to a separate deposit. I list these in the Checking Account like this:
DATE  NUMBER  DESCRIPTION                        TRANSFER        DEPOSIT
Date  0012    Deposit  #123456   Total $225.00   Misc. income    $75     
      0012.1  Deposit  #123456a                  John Jones      $100
      0012.2  Deposit  #123456b                  Tom Smith       $50

I use the number column as the sort, to make sure all the entries to a single deposit are kept together, and show the actual amount of the deposit in the description field.  A 3-level split would enable me to use the deposit as the 3rd split, and all the separate donations could be added in the single deposit.

The Debit card 3-split would allow me to transfer debit card transactions directly to the Checking account, and still have separate labels for direct transactions to the checking acct and for the debit card.