On the Layer II Toolbar are some companion icons. LAYISO and LAYUNISO. Selecting LAYISO (the one on the left) will isolate all objects on one layer.
After selecting one or more objects, all layers except the layers of the selected objects are either turned off, frozen in the current layout viewport, or locked, depending on the current setting. The layers that remain visible and unlocked are defined as isolated.
Locked layers are dimmed by default. But by typing in “S” for settings, you can specify the percent of the dimming from the Lock option in this command (I like 75%). You can also change the value with the LAYLOCKFADECTL system variable.
If you make changes to layers within a session and you want to restore the layers to the state they were in immediately before you entered the LAYISO command, use the LAYUNISO command (the one on the right).
There appears to be no undo stack on this command. So once you isolate a layer, you need to unisolate it when you are done. Do not move on to another isolation. If you do, you can however use Layer Previous to step back through these layer changes.