There is a Goerli testnet version of the Creator Toolkit that you can find here. You can also access it through the dropdown menu on the main page.
The Goerli testnet is mainly used for blockchain testing before deployment on the Ethereum mainnet. Using the Goerli testnet you can create test versions of your Drops or Editions collections; because it's a testnet, the currency is worthless.
** To use the Goerli testnet, you will need to ensure you have swapped networks in your wallet **