Does LNM read scenery that is disable in AL? 

Depends on whether you added the directories of disabled scenery to be included in LNM scan. If LNM doesn't know they are to be scanned it won't scan them unless they are in the community folder. When you open the Load Scenery window you'll see a base path - mine is set to MSFS Pckages folder which contains Community and Official folders - these and the folders within them are the only folders LNM will scan UNLESS you add additional folders in Tools; Options; Scenery Library Database.

I assume one could set LNM to scan only Official and not Community and then add a folder or folders containing all addon scenery and then LNM would scan all Official and all addons whether the addons are active or not. I considered doing this, and maybe will in the future, but for the time-being I simply activate all addons using Addons Linker before an LNM scan.