New to Xcode 7.3 beta, you can select Preferences > Components > Toolchains without having to launch Xcode from the command line.
Things that you probably figured out on your own:
- You can’t use beta toolchains for App Store compilations
- The Playground is limited to the default toolchain. (And they’re still a bit laggy for massive playgrounds.)
Things you might not have thought of but are worth knowing:
- The code migrator doesn’t work with beta toolchains. It’s strictly limited to the default toolchain.