Composite Images button in toolbar shows this dialog.

This dialog allows you to composite current image with previous one.

For example, when you have a screen shot of a menu dropping down, and previous item was for whole window, you can composite these two items to generate an image of whole window with menu dropping down.

• Increment the image composite level adds one more item to composite.
• Decrement the image composite level removes the first item from composition.
• Clear the image composite level removes all items from composition.

For items with composite level set, yellow arrows appear like .