Magento: Add fields to the Admin Backend

Today I had a task at work that first sounded rather easy: Add a field to the Admin backend, namely System->Config->Catalog where the user could later insert some SKUs to control which products are shown on the home page. The first resources I found on how to edit the Backend where all suggesting to create a Module and then create a settings page. Not only was this rather complex it was also way too “over engineered” for a simple thing like a text field.