This command is usually grayed out. It becomes active if you use the Fill function or the Blend tool, or if you apply some filters.
It allows you to modify the paint mode and opacity of the last drawable operation (Fill, Blend, Filter) by creating a blend between the current state of the layer and the previous state. It performs the following operations: copy the active drawable, undo the last action, paste the copy as a new layer, set its “Opacity”, and merge both new layer and previously active drawable.
This command brings up a dialog window:
This drop-down list allows you to choose a Layer merge mode.
This slider value is initially set to the opacity of the color you used with the Fill or Blend tool, which corresponds to the current state. Lowering the opacity to 0 changes the drawable to its previous state. Intermediate values produce a mixture of the two according to the mode you have chosen. The effect of this setting is visible in real time in the image, but you have to click on the
button to validate it.