When adding new displayoptions with an option id <200 a button will appear in the button tray.

Depending on the value in "Default label" the bitmap changes. For example if the default label is "Relate to release" then the bitmap displayed is the "linked chains" bitmap. If the default label is "Remove link" then the bitmap is a red x.

But I can't find where the bitmaps are stored. I assume it is the word "Relate" & "Cancel" that trigger which bitmap to use. So I searched the client installation "*relate*.*" and found trelate.gif but this is different from the bitmap that is displayed. So where is the bitmap that is used and how can I control which bitmap to use?