I'd like to produce a report that checks all the nodes for resources that aren't selected; so for example
Applications
CPU & Memory
Volumes
Interfaces
Is there such a way to do this?
To the best of my knowledge, no, you cant create a report for this as SolarWinds doesn't store the info that it doesn't monitor.
The only possible workaround that I can think of is mentioned below:
Explore Settings -> Network discovery (Network Sonar Discovery), if you have an iterative discovery schedule setup without automatic addition, you should be able to view new nodes, new interfaces and new volumes discovered under Scheduled discovery results (but then again I am not sure if this can be pulled over a report, but its available on GUI for you to see).
Forgot to mention one point, this doesn't consist of everything that you are looking for, this will only give you the core elements which is (Node, Interface, Volume).
For CPU, Memory you will need to check from Settings -> Manage Pollers
Applications again in SAM - AppInsight supported.
Again as mentioned above, there isn't a straight forward approach to achieve what you are looking for.
Hope this helps.