You can also import a single, high-resolution icon to let the editor fill all the icon placeholders with a scaled down version of the imported icon. For this, select the Import a single high-res icon from the top right toolbar of the editor. A wizard will be opened where you can drag and drop an image from your local filesystem. Be aware that only PNG images are supported. After dropping this image, you can preview how the image is scaled down into a variety of sizes at the right pane of the wizard. If you are satisfied with the resulting quality, click the finish button to end the import. Optionally, you can select if this icon should be used for every or a particular platform.