The Isolate Button at the Top of the View Filter Manager - you can select a Layer or an Object graphically and select the Isolate Button and then when you tap the Isolate Button again it changes back to the prior view. While one layer is Isolated, you can use Up and Down Arrow Keys to scroll through one layer at a time isolating the selected layer (the arrows move the layer selection up and down). If you hit the Space bar while a layer is Isolated that will turn the layer off so once it is "unisolated" it will be hidden. Use this to work through a CAD file to determine which layers you need / dont need and then you can use Invert to show the Hidden Layers - Select the data and Delete it or export it to a VCL so you have a backup of the deleted stuff should you need it.
Alan