You can create a new group, then use 'include material' if there is a material such as 'leather'. Beware using the dreaded group tool however if you are doing anything for sale. It has bugs and the store may reject items on which the group tool has been used because 1) it embeds geometry in the cr2 file (a bunch of v and vt lines where there should only be deltas which violates copyright if it's not your object) and 2) Causes bugs in pro pack in the form of missing parts or holes in the mesh.

"Your work is to keep cranking the flywheel that turns the gears that spin the belt in the engine of belief that keeps you and your desk in midair."

Annie Dillard