Deleting items in lists is currently only possible by the selecting Edit -> Remove in the menu or doing right-click -> Remove. It would be nice to have a keyboard shortcut to delete items too. The 'delete' key seems an logical choice, and would mimic the behavior of deleting files on the GNOME desktop.

Deleting an item from the library should probably bring up a question dialog to choose between 'remove' and 'move to trash', which would also act as a confirmation that prevents unwanted removals. Deleting an item from playlist would not need this question dialog, since 'remove' is the only available option there.