The fuel slot menu can be used to create fuel slots for a custom container. Fuel slots have a name, a fuel registry, and a placeholder. The name is used to distinguish fuel slots from each other and to link them to fuel indicator slots. The fuel registry determines which items are considered fuel and how long they keep it burning. The menu should look like this:

• The 'Cancel' button will take you back to the container edit menu for the container you are editing, without adding a new fuel slot.
• The 'Apply' button will create the new fuel slot (if the name and fuel registry don't have any validation errors) and use it to replace the old slot (you came to this menu by clicking on a slot, which is the one that will be replaced). It will also take you back to the container edit menu you came from.
• You need to give the fuel slot name and insert that into the text edit field on the right of 'Name:'. No two fuel slots in the same custom container can have the same name. Oter than that, it doesn't really matter what name you give, but I recommend using logical names if you use more than 1 fuel slot. Currently, the name of fuel slots will not be shown or used in-game.
• You also need to give the fuel slot a fuel registry. This fuel registry will determine which items players can use as fuel, as well as how long they keep this fuel slot burning. If you use multiple fuel slots, they may use the same fuel registry, but this is not necessary. There should be 2 buttons on the right of 'Registry:'. The first button shows the name of the currently selected fuel registry, or 'None' if you haven't selected one yet. Click the button to change it. The 'Create new' button can be used to create a new fuel registry (and you need this if you haven't made one yet). The button will take you to the fuel registry edit menu, where you can create it. After creating a new one, you should be taken back to this menu, but you will see an extra option when you click on the first button. Currently, you can only use your own fuel registries, so not minecrafts default ones.
• The Placeholder will be displayed in the slot when no fuel is currently in the slot. Click the Choose... button to choose the placeholder and click the Clear... button to remove it. Note: the placeholder is optional!