You can install QtCreator inside Scratchbox.

To start QtCreator on your main screen instead of the Xephyr running your SDK, you have prefix the DISPLAY environment variable to 0.

For example:
QtCreator runs completely in scratchbox. When you start your application with it, first go to your "Projects" tab on the left and look for the environment to start it. Change the "DISPLAY" there to ":2".

PS: I have the issue that QtCreator (and even the installer) don't show a cursor for me when running it like that. But I've never received a solution for that by anyone ....