Content Filters 
The content filter is accessed through the Content Filters dialog box.
Name filter
Use wildcards to select content items by name.
Invert
Reverse the name filtering.
Clear
Clear the name filtering
Show unassigned materials
Displays materials that are not assigned to objects or layers.
Show V4 materials
Displays materials that were created in Rhino V4.
Show hidden materials, environments and textures
Displays items that are hidden by their rendering engine.
Show reference materials, environments and textures
Displays items that are generated by worksession references or linked blocks.