When one first creates a new project, that dialog lets you point to some external .PNG file, and then when that dialog completes, it generates 4 different pixel-sizes of ima
I can confirm that in Android Studio 1.x (here AS) on Windows also the right sequence is:
This can be done absolutely in any moments after creation of the project.
Android Studio warns you that it will overwrite the current ic_launcer, but this is exactly what we expect to do.