According to a tool tip in the submission section, if enabled, a submission will be used for direct item removing. There can be at most one item remove submission per app. The access level of this submission will determine who will be able to remove an item. You'll also have to assign an ItemRemove Element to the layout you want the Remove Item button to show on.
You need set Item Edit to Yes in a Submission settings of an application. Also check right access level.
On all questions it is best to contact the support forum.