Getting logging from Qt Creator would require you to set the environment variable QT_LOGGING_RULES=qtc*=true.
On Windows you would need a tool like Debug View to see the debug log.
Alternatively Qt Creator has in Tools > Debug Qt Creator > Show Logs....
You could try starting Qt Creator with controlled plugins that get loaded:
$ qtcreator.exe -noload all -load Core -load QmakeProjectManager ...
This way you could find out if there is some plugin that does bad things.
Lastly, use Process Explorer and / or Process Monitor to find out what Qt Creator is doing under the heavy load.
The best option would be to have a profiler on Windows to analyze what's going on. But the usage of ETW is a skill in itself.