hmmm… After a few searches, I found this gem : material_selection.rb (1.8 KB)
it allows you to select the same material among model, even inside groups or components. careful though. because it selects faces inside groups as well, use with caution (for example, grouping the selection would cause unexpected behaviour). But you can then use thomthom’s plugin listed above to hide everything that is unselected, perhaps other manipulations that i’m not thinking of right now.
Note that it’s a rb file and not rbz. You won’t be able to install it through the extension manager, place it in your plugin folder. (and restart sketchup)
to then use it, once the desired material is ‘loaded’/selected, go to extension menu > material selection