ButterKit is described as 'Helps app developers reach more users faster. Quickly create stunning screenshots for the App Store; capture straight from Xcode Simulator, edit with 1-click templates and 3D devices, localize to all 39 App Store Connect languages, and upload/export' and is an app in the photos & graphics category. There are six alternatives to ButterKit for a variety of platforms, including Mac, Windows, Web-based, iPhone and iPad apps. The best ButterKit alternative is Penpot, which is both free and Open Source. Other great apps like ButterKit are Affinity, Canva, Figma and Sketch.
ButterKit helps app developers to create App Store collateral. It is not a graphics tool per se.