I am looking into customizing the 'List Resources' page. Is this even possible? If so, are there any resources I can read about how that page is created?
The list resources page cannot be customized the list Resources run against the node, it will send an SNMP request against the node to show all the resources that can be monitored what are you trying to accomplish?
I have a few things I am trying to tackle and maybe I am looking at this incorrectly. First, a lot of the interfaces on the list resources page are things that dont need to be monitored and I would like to simplify that page so that they arent there at all. Secondly, not all of my devices have an option for Asset Inventory. I would like to flesh out the asset inventory queries and create that as an option on that page
Unfortunately none of what you are asking is doable, the contents of the list resource page are generated dynamically when you click the button and there is no mechanism to filter away the types of objects it tries to find or add in objects that it does not find. If a feature like asset inventory does not come up then Solarwinds did not see the markers it is looking for to indicate that the feature would work.
mesverrum is right, you can't simply customize the list resources page. Orion runs a lot of action in the backend to produce all the resources it can show to you as options. Also, to understand how asset inventories work, you can check this post: Re: asset inventory - what is it using? Some of your devices are probably not covered by this feature.
Also just because they show up on the list does not mean you need to monitor them just select the interfaces that are important to you and the rest will not be monitored.