Isolate object(s) is totally useless without transparency option. We need x% (e.g. 50%) transparency for the rest of the objects to create proper context for editing isolated object in relation to other objects.
Editing objects in blind mode (without transparent background object) is counterproductive: Isolate , edit object, unisolate, the edited object is too big, isolate again, edit again, unisolate, edited object is too small, isolate again, edit object again, unisolate, edited object is (maybe) fine.