If the top level tabs have been docked at custom locations, this will reset all of them back to their default location. Note that the mechanism Qt uses to do this is somewhat buggy, so they might not always end up exactly where they started. In that case, just manually adjust them to your liking.
Toggle between showing the xforms and optionally the grid with no image, and vice versa.
The scale used to draw the xforms can be adjusted by scrolling the mouse wheel while holding the Alt key. This button resets that scale multiplier to its default value of 1.