Mark Bank Import Transaction as Inter Account Transfer

By using a transaction clearing account - read below

You need to create bank rules which post the imported transaction to a transaction clearing account.
Import the Bank Statement and the Spend Money to the Credit Card gets debited to the clearing account.
Import the Credit Card Statement and the Received Money from the Bank gets credited to the clearing account.

Read the below modified extract:
The imported statement entry relating to transfers between financial accounts needs to be processed with a Bank Rule via a clearing account. (Or edit the entry to the clearing account)

Bank/Credit Card Transfers are two separate accountings transactions not a single transaction.
1.Bank: Spend Money - Credit Bank and Debit ???
2.Credit Card: Receive Money - Debit Credit Card and Credit ???

The Inter Account Transfer feature in Manager allows you to truncate that to a single entry - Credit Bank Debit Credit Card.

However, when importing financial statements the processing of two transactions is still required because (rightfully) Manager’s Bank Rules prevents any allocation directly between financial accounts otherwise you would have duplicate transactions as demonstrated below.

If you substituted the ??? for the opposing Bank/Credit Card account you would now have:
1.Bank: Spend Money - Credit Bank and Debit Credit Card
2.Credit Card: Receive Money - Debit Credit Card and Credit Bank

The Bank account now has two credit entries and the Credit Card account now has two debit entries - hence the duplication. So to use Import Bank Statement you just need in the Bank Rule to post the opposing debit/credit entry to a clearing account, where the contra transaction will cancel themselves out.
1.Bank: Spend Money - Credit Bank and Debit Clearing Account
2.Credit Card: Receive Money - Debit Cash and Credit Clearing Account

The Clearing Account can be created as either a Current Asset or Current Liability