The one sided entry is simply posting an entry to CM as normal but then you tab down to where you would put in the GL and amount highlight the top line by clicking the far left side of the line and hitting the delete key. For example my payroll company sends an automatic GL entry that breaks out my labor into the different ledgers. But for me to reconcile to the bank I have to make the one sided lump sum on the CM. So I go into CM and do new-withdrawal, enter the date of the payroll, enter the full amount that was credited from my bank account, tab until I get to the Ledger/Description/amount lines (It is weird if you don't tab down into it, you cant delete it) click the far left of the line and hit delete. This creates the necessary entry to the CM that will balance to the GL and I can reconcile with the bank by clearing in CM.
It will give an alert when you hit save saying there is no balance to the entry, but it is just the one sided entry to balance the GL/CM and Bank.