To delete storage bins, go to Lagerhaltung (Inventory) → Lager und Lagerplätze (Warehouses and Storage Bins) and first select the relevant warehouse. You can now delete an individual storage bin via the context menu.
Alternatively, you can select multiple storage bins using the checkboxes and then delete them.
Just like with warehouses, storage bins cannot be deleted if they still contain products with stock, or if they are the default storage bin. In this case, you'll also see a corresponding error message when you try to delete the storage bin. If this happens, the products must be relocated, or a new storage bin must be selected as the default storage bin.