The vertical toolbar option used to add a military treatment facility (MTF) item to a customer's catalog is?

The correct choice for adding a military treatment facility (MTF) item to a customer's catalog is related to the specific function within the system that allows users to customize their catalog to include such items. Typically, the term associated with adding custom items is "CUST," which stands for "custom."

Using the "CUST" function allows for tailored modifications, enabling users to include specific MTF items that may not be found in the standard catalog. This ensures that the catalog reflects the unique needs and inventory of the military treatment facility. The emphasis on customization highlights the importance of having the ability to manage and curate specific entries based on particular requirements or preferences.

In contrast, the other options such as "UPDATE," "ADD," and "REMOVE" would typically refer to altering existing items, adding new items broadly, or removing items from the catalog, rather than focusing on customization for military treatment facilities specifically. This further clarifies the relevance and appropriateness of using "CUST" for this task.