I have a very similar problem. The credit cards are from Bank of America.  There is the main and two employee ones.  All three are connected to QuickBooks Online.  In Chart of Accounts it will not allow me to put the two employee ones as a sub under the main account.  Each account receives a bank balance.  I have read that the parent account should not be connected, however, if I disconnect it what do I do with the small amounts of interest earned, etc.