How to merge two credit card accounts

• Back up your data file in case something goes wrong or you don't like the end results.
  
• Left click on the oldest dated  transaction in a register that you want moved to another file.
• Scroll down to the newest dated transaction in the register that you want moved and then Shift+Left click on it.  Now those two transactions and all the transactions between them will be shaded.
• Right click anywhere on the shaded transactions and click on Move transaction(s).
• From the drop-down in the pop-up, select the account you want the transactions moved to.
• Click OK to start the move transactions process.
  

One thing you will want to make sure to do:  If the account you are moving transactions from has the older transaction dates and older Opening Balance transaction, be sure to include that Opening Balance transaction in the transactions to be moved.  Also, make sure that the Opening Balance in the other account is deleted.