If the crypto is in your own hardware wallet or software wallet that you control, then simply create a Minute documenting the exchange of the title of ownership of the crypto into the trust. And list it on Schedule A in the trust. That's it.
If the owner is concerned about the tax man charging one with taxes on capital gains, one could notarize the Minute and provide a copy of it later on to the tax man if one is ever assessed for capital gains. The notarization proves on public record the date of the transfer to a nontaxable entity.
A hardware or software self-controlled wallet is how the majority of the savvy crypto owners store their crypto. It is well known in the crypto world that it is high risk and not recommended to keep much of their crypto residing at an exchange. It is not recommended to keep large amounts of one's crypto residing on the exchange servers. One of the main reasons people got into cryptos is their decentralized control and the ability of the owner to control his own storage of the currency, unlike banks.
But if the owner wishes to keep one’s crypto on an exchange, then one would need to open an account at the exchange in the name of the trust and transfer one’s currency into that account instead of the account in one’s personal name. This is just like opening an account at a bank for the trust in which dollars reside. It is only a matter of the owner of the crypto opening a separate account in the name of the trust, and storing the crypto in that account.