The Upgrade: Cart Modifier allows the player to modify carts when it is attached to the Cart Assembler by placing it on one of its sides. To modify a finished cart, put it in the Cart Modifier upgrade's storage and open up the Cart Assembler interface. The cart and all of its modules will be shown. The player can switch which modules they want to keep and remove by clicking on them. If a module is red, it will be removed once "Modify" is clicked. Modules can be added in empty slots. Installing new modules will take as much as time as normal installation and removing modules will take time. Once the cart has finished being modified, all removed modules can be found in the Upgrade: Cart Modifier's storage.