How can I remove the Approve/Reject menu item in the Actions menu? This item is present under Project info > Documents > Actions and on the document level itself in case an Approval Cycle has been setup.
The fly-out or Actions menu cannot be customized using the Menu Builder (for now).
You can only customize the Main menu, Project Details menu and Document Details menu. The last two are the sub-menus (not fly-outs) you see when you open a Project or Document.
The Approve/Reject option cannot be removed from the Actions menu.
However, even though you are able to select multiple documents and click the Approve/Reject link, the action itself will not work on documents that are not assigned to you to approve.
For more information on creating custom menus, read the Create a Custom Menu section in the WebCenter User Documentation.