[Zope] Cannot add an Edit tab to the management screen

Hello, I do not see an 'Edit' tab appearing in the management screens of my (python) product with the following instruction: manage_options = ( {'label': 'Edit', 'action': 'manage_editChannelForm'}, )+ObjectManager.ObjectManager.manage_options +RoleManager.manage_options +Item.manage_options Could you tell me what is wrong or what else in the code has to be checked to make it working ? Thanks in advance, Philippe