If we select the relevant to cash flow check box it will determain that the GL account is related to Cash receipt account / cash disbursement account and the same can use to make out going payment through either cash or bank.

And it can usefull while making cash flow statements.

If not select the relevant to cash flow check box while creating GL Account related to Cash or Bank

We can post the vendor document in F-43 and it allows to make outgoing payment entry through F-53 also

But we can run the manual check number from the register

It will through the error message "the particular document no is not a payment document