The idea of transforming the selection box in the graph editor similar to how it works in Photoshop is an interesting suggestion. Currently, in Spine, you can manipulate the selection box in the graph editor by holding the box selection for a second, which allows you to scale the keys. This functionality is similar to the mechanics used in the Dopesheet and Graph, where you can scale on both the X and Y axes. While the specific feature you mentioned isn't available yet, the existing tools provide some flexibility in transforming selections.
