I think you may be confusing two things – blockchain addresses and their permissions, versus blockchain nodes and their API credentials. You can have multiple addresses on one node, and you can have multiple nodes sharing addresses. But this has no relationship to the access to each node's API, which is used by multichain-cli.
But each node run in its own blockchain directory (see the datadir runtime parameter) and has its own passwords for connecting to its API, as set in the multichain.conf file.
The top of this page should provide you with some more guidance: