To step and repeat the heart, I selected the heart layer (this is a pixel based layer, not a shape).
Command + Option + T (Mac) | Control + Alt + T (Win) transforms a duplicate of the layer. In this example I scaled the heart down and moved it to the right.
Command + Option + Shift + T (Mac) | Control + Alt + Shift + T (Win) duplicates the layer and applies the same transformation settings (step and repeat). I this case I applied the shortcut 4 times.
Here are a few additional examples. The first heart layer was scaled down from the center, and the second shows the heart moved and rotated when duplicated.
Use Command + Shift + T (Mac) | Control + Shift + T (Win) to transforms a layer using the previous transformation settings but without making a copy (this is the same as Edit > Transform > Again).