I just installed AI 2022 26.0.3 for Windows and noticed "DebugPanel.aip" in the Plug-ins folder. Thank you, Adobe, for bringing this back! I don't see the familiar graphical object heirarchy, but it's still very useful.
The keyboard shortcut for it is found/set in custom keyboard shortcuts for Menu > Other Panel > Debug Panel. It now uses F11, rather than the F12 from CS5 and earlier.
I also have 26.0.3 for Mac, but don't see it there. Is this plugin Windows-only?