You can have 2 nodes running on the same machine. The basic idea is to create a second directory and run multichain from there as a second node. So once you create the 2nd directory with the name, for example, multichain2nd go inside the directory and execute the command:
multichaind -datadir=<your_path_to_multichain2nd_directory> -port=10255 -rpcport=10254 chain0 -daemon
This example resumes that you chain name is chain0.
From there you have to set permissions and so on...
I have posted an article on Dzone for this. A how-to guide for 2 nodes on the same windows machine.
https://dzone.com/articles/how-to-get-started-with-multichain-blockchain-on-w
Just found that it has already been answered before :)
https://www.multichain.com/qa/2817/how-to-run-datadir-in-multichain?show=2822#a2822
