Edit/Undo
Undoes to the last drawing.
Edit/Redo
Redoes the last drawing (after an undo).
Edit/Swap colors
Swaps the last used two colors. Comes handy when working with an outline: you can swap between the foreground and background colors easily.
Edit/Scale image...
Scales the image (See Scale and expand image window).
Edit/Expand image...
Changes the canvas size (ie. changes the image size withouth changing the pixels) (See Scale and expand image window).
Edit/Apply ink
Applies the current ink on the image. It's the same as if you were drawing a rectangle covering the whole screen. This function is helpfull to clear quicly the screen, or the make the whole screen blured, lighter, etc.