Hi Lauren, I think the main difficulty to allow card via scan only is: for POS scan and card entry via keyboard are the same event, there is no difference (because loyalty scan works similar to product scan/customer ID scan/discount coupon scan).
What barcode scanner type do you have?
1) Is it OPOS or just a keyboard emulator? If your scanner is OPOS, then via Extension can be theoretically possible to distinguish scan and keyboard entry...
2) if your scanner acts as keyboard emulator - then how POS can distinguish scanner and keyboard? Both devices act as keyboard.
POS extension can be done the following way
1) Forbid scanning loyalty card at all in POS
2) Developers will create new operation and dialog 'Scan loyalty card' - this dialog will not have any input fields, but will be listening to 'on barcode read' event - without input fields manual entry is impossible, only data received from scanner will be put into dialog and when data is received - execute operation 'add loyalty card'