Are there any documentation on SSCM, or at least a way to add a plugin to the Admin page. The example shows how to add a Group/File to the client page. But I would like to add it to the admin page instead,

Is this what you are looking for?

https://doc.developer.milestonesys.com/html/index.html?base=samples/downloadmanagerclient.html&tree=tree_1.html