I have looked in several Filemaker books for this answer for the last six months and I cannot find it. Please be advised that I work exclusively in FM11, so I do not know if the below information is true for other versions of Filemaker.
In Layout mode, on most fields in the lower right hand corner there is a "lollipop icon" for want of a better term. As far as I can tell it does nothing. If I click on it nothing happens, if I double-click on it, nothing happens. If I attempt to drag-n-drop using the icon, the mouse behavior is ignored, or rather, the whole field is moved, but I can get the same behavior by clicking on any part of the field.
The only clue I have that it might mean something is that when the field is from an internal table, the lollipop is green and when the field is from an external table, the lollipop is yellow. I do not know if that is coincidence or if the different color has a different significance that only by chance happens to match internal/external divisions.
What is this icon for?