v3 Soften Tool

The soften tool softens the selection edge (not the image itself). This is useful if you have soft edges to objects because they are out of focus, for instance. If you find you have softened a selection edge too much, you can unsoften with the unsoften tool. The Radius slider affects how much the selection is softened.
Repeatedly softening an edge can also progressively make a selection edge softer.