In the book it states:

Sidenote: there is an inherent difficulty which arises from this situation. You need to send the newly created, unsigned multi-sig transaction to every signer and after their signed it, you also need to collect the partially signed transactions from them and combine them into one, so that you can publish that on the network. This problem is partially solved by theBIP-0174, because it at least standardizes the data format, but you still need to implement your own way to distribute the data between the signing parties.
NBitcoin doesn't have an implementation for BIP-0174 or for the off-chain data distribution yet.

Could you please update this section to support PSBT? Scenarios like partially signing a multisig transaction and create its PSBT(and send it to other cosigners), and also further partially signing a PSBT sent to us, and at the last to sign and finalize the PSBT.
Thanks in advance.