I've thought I've seen all, now the Debug View Hierarchy button has decided to take a hike. One of XCode's coolest features just upped and vanished on the latest project. Shows fine in the previous two. Can't find anything that looks like an on/off switch for the thing and have capabilities and debug settings matched to the ones that work. (and yes, I am in debug mode)
There are a few options in your target's scheme to verify. The first, under Info, is that Debug Executable is checked. Without this, none of the standard debugging capabilities are available, including LLDB and the view debugger. The second one to check is under the Options tab, and verify that "Enable user interface debugging" is enabled.
— Ed Ford, DTS Engineer