There are various notes I need to associate with different devices on my network, is there any way to capture this information in System Center Essentials?
I have used systems like SpiceWorks where I can add additional info to any object, say support contact info, notes on non-standard setup or configuration and why it was done, things like that. Can this be done out of the box with System Center or is there a plugin to allow it?
Not really. You could add a custom attribute, but that would have a max character length (255) that might be restrictive. What you’re asking for is really a job for a CMDB like Service Manager 2012. In that case, you’d likely need to move to OpsMgr 2012, for which Service Manager 2012 has a connector to auto-populate it’s CMDB with data from OpsMgr, AD, ConfigMgr, etc. At that point, you can add notes all day long.