If you're trying to withdraw from a pool on Curve Finance that is not displayed, you can still do so by interacting with the contract directly. You can use a platform like Etherscan to do this, which will give you access to the contract address and allow you to interact with it. You can then use the contract to withdraw your tokens from the pool. Be sure to double-check the address before you interact with it to make sure you're sending your tokens to the correct address.