Although it is obvious that you can create transaction images yourself in the Pictures/Transactions folder (see also The Pictures Folder), MoneyWorks won't "see" the picture unless the fHasScan flag (= 0x00100000) is set in the flags field of the transaction. This is an optimisation to save MoneyWorks the considerable expense of testing for a transaction image every time you open a transaction.
MoneyWorks 6.0.6 adds a method of synchronising this flag if you have added or removed a transaction image behind its back.
evaluate "SyncTransactionImage(trans_seq_num)"
The SyncTransactionImage function (available only to the evaluate command) will check to see if there is an image for the transaction with the given sequence number and set or reset the hasImage flag as appropriate (provided the transaction is not locked). The function returns 1 if there is an image; 0 if there is not.