There is not any official desktop GUI for building with the Spark Core. There are a few different ways that are available for doing so, but they do require a bit of setup to get going. You can use any IDE that you would like, but building and flashing aren’t quite as one-click as the Arduino IDE. The Spark CLI makes things a lot easier, but it’s still all done on the command line. I can’t say that I blame you about not wanting do go through that hassle. I know how to do it, but I’d also rather not sometimes!
In the meantime, there is an article written in the forums for Installing the USB Driver on Windows & Serial Debugging (assuming you’re using Windows). If not, let us know and we can help steer you towards the easiest options for your operating system.