Lets make it simple, lets say I want to have a per sidebar setting that will control if the sidebar has a white or gray background.
Obviously I can add some CSS to do that, but I want to let the user decide about it, without forcing him to learn CSS.
It is possible to have a "parallel" configuration screen for the sidebars themselves, but this make a bad UX as it basically forces the user to have two windows open to have all the context while configuring sidebars and widgets.
A better approach will be to have some section below the sidebar description, but there doesn't seem to be any simple way to do that.
Have I missed anything? I am open to other UX ideas as well.