You must be using Revit as Isolate is a Revit feature.
But you are correct, it is possible in the 3D Window but not possible in the Floor Plan. In Floor Plan, when a Layer is visible, all elements on that Layer are visible.
I guess the whole rationale behind Layers is that you create Layers based on what groups of elements you want to see and not see together. So in ArchiCAD you would solve this with Layers.
But I understand your point that it is sometimes handy to be able to show only the specific elements you are interested in without the visual interference of other elements on the same Layer.
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