Having an issue with illustrator when I use the keyboard shortcut for isolation mode. If I use it the first time on a set of objects, it works. But when you're in isolation mode for that object, if I try to enter isolation mode again for another set of nested objects it doesn't work. I want to set it up so Control + D goes into isolation mode over and over again so I can drill down to the set of objects I need in artwork. I think this is a bug
You could enter isolation mode & then use the Select menu options to drill down further. Like all text objects or all objects with the same stroke within your isolated ones. Its not exactly "nested isolation mode" but close enough. Note that you cannot isolate a bunch of objects unless they are grouped.