Sometime you just want to quickly try some code, which can be done in a project, like in a Load event of a Window, but that is a bit cumbersome.
Maybe a simple "playground" window would be nice to have. For me it doesn't have to be as fancy as the one in Xcode. Just a simple code screen with a fixed console output section at the bottom.
And maybe also a way to save "playground" code screens, so that you can make a library of test code.