Add notes for the plugins on your Confluence. They will be visible to all administrators. Next time you will need to renew the license, you'll be able to find the required information.
New notes appear within seconds once your colleagues add or update them. Collision detection keeps your notes safe after you have submitted them.
Admin Notes are stored in a file in Confluence Home directory. You can peek in the file even if Confluence is not running. It's the easiest way to copy information between instances.