Undo Isolate
This article explains the Undo Isolate button found in the ClearEdge3D tab.

Able to Undo Isolate

Unable to Undo Isolate
The Undo Isolate button reverts the current view to a state before any single or multiple isolation actions were performed in a row. This removes the need to Undo multiple times to revert to a non-isolated state. If you only want to undo one isolation, the Revit undo button or using (Ctrl + Z) will perform that function.
The Undo Isolate button performs the same function as it does in the Modify Tab.