Discrete Manufacturing- Unable to Add Scrap Material as By-Product in Work Definition (Redwood Page)

Hi,

In Discreate mfg, we're planning to bring scrap material as a By-product in our production process. Specifically, in the Redwood page under the Work Definition module, on the Operation Output tab, we are trying to add the output item for scrap material. However, no item is appearing in the list to select.

Could anyone guide me on how to define item in the Operation Output tab?