I know this thread is a bit dated, but I had this same issue and wanted to share my solution.
I used the ‘Capability Manager‘ plugin.
Once activated change the settings on the ‘Capabilities’ page under the ‘Users’ menu.
Select the ‘Editor’ role to edit and tick ‘Edit theme options’ before saving.
The ‘Editor’ user type now can add/edit ‘Widgets’ and ‘Menus’ under the ‘Appearance’ menu.
They can also view the current theme, but cannot change or edit it.
Hope this helps!
