This has been removed. With TRS2009 and up, there's a Pick List. It's under a filter icon on the title bar in Surveyor. It looks like a funnel and is located next to the Quick Drive which I always click by mistake. Anyway drag the textures you want to use all the time into the pick list area and they will be yours to use all the time going forward. You can add other stuff too such as commonly used trackside objects, road splines and other assets.
Sounds like you need to enable compatibility mode in your browser - it's in one of the menus, or in the form of an icon on the right of the address bar.