Multi-discs within Launchbox are called Additional Applications. Examples of the data xml can be found here: https://www.dropbox.com/s/8n9wwqvrqafnc0f/Sony%20Playstation.xml?dl=0 (there's a lot of redundant additional apps here due to Launchbox adding all the videos from my media folder by accident, but look at Final Fantasy VII as a good example).
Multi-discs within Launchbox are called Additional Applications. Examples of the data xml can be found here: https://www.dropbox.com/s/8n9wwqvrqafnc0f/Sony%20Playstation.xml?dl=0 (there's a lot of redundant additional apps here due to Launchbox adding all the videos from my media folder by accident, but look at Final Fantasy VII as a good example).