Select items to be shown in sidebar

it's already the case.
Most of the entries in the sidebar are plugins. Each plugins register their own entries. So if you don't want some entries just disable the plugins. If a category don't have any entry then they are not shown.

Play Queue, Internet Radio, and Podcasts are not plugins.

To make hiding things simpler, I'd say to right click the sidebar then choose "Edit Sidebar" or something. Then checkmarks would appear next to items and you could uncheck them to hide them. All of the text would be grayed out to show you can't click them. At the bottom of the sidebar there would be a "done" button to save the changes and stop editing.

Or, the toolbar editor could be renamed to "App Editor" or something (probably something else, App Editor sounds like a development tool) and would trigger editing both the toolbar and sidebar to streamline the whole process. It'd be nice if the toolbar part worked like it does in Eye of GNOME and Evince. Dragging and dropping toolbar items is alot easier.

John,

hmm Yea you are right. Putting the app in kind of an edit mode all around would be interesting.

the toolbar editor comment is kind of off-topic, but if someone would code it then I'm almost positive it would be merged in :)