Order entry is built around product menus, and the same screen behaves differently depending on how the enterprise has configured it.
Change quantity, add bulk quantity, duplicate an item, convert an item to a variation, convert item size, convert an item to a combo meal, convert child item size, delete an item, add, edit and delete item level comments, apply and remove the kitchen hold flag, change item price, look up a product, view product details, scan or type a barcode.
Order Entry Overview, Enter Order and Item-Level Procedures.
Source: Global Payments / Xenial Enterprise POS product documentation. Enterprise sites are heavily configured, so confirm the exact behaviour against the customer own build before advising a change.