Once in the edit mode of a standalone Learning Item, you will be able to delete the item.
On the top right-hand side of the editor, under the ellipses, the 'Delete' button exists.
If this learning item is published, you'll be shown a confirmation modal to unpublish the learning item first.
Once you confirm to unpublish the learning item, you'll be shown a confirmation modal to delete it.
Upon your confirmation, your learning item will be deleted and can not be retrieved.