It is not possible. It is better you also buy seperate hardware wallet each to create the multisig wallet.
Concerning the question, this Coldcard FAQ would be helpful:
Can I have multiple wallets in each COLDCARD?
There is a single "wallet", derived from the BIP-39 seed words. In addition, we have an optional "duress" wallet, which is derived from the wallet's seed words and is not independent. This means it gets backed-up automatically, and the original seed words also backup the duress wallet.
By adding a BIP-39 passphrase you can unlock nearly unlimited additional wallets which derive from the original 24 seed words. The passphrase you use defines the wallet and cannot be changed. BIP-39 passphrases are not backed up or otherwise tracked, which gives lots of freedom in terms of plausible deniability.
Note: creating multisig wallet with you having the co-signers on the same wallet is not secure, not advisable as I have mentioned before.