The red triangle on the Record List Campaign layout is indeed a button and I can double click the button while in layout mode to open button setup...
If I make a copy of it and ungroup it twice, I find that it is made of two objects, the triangle graphic and a transparent rectanble. Such rectangle objects are tricky to select, you may need to drag a selection box around it unless you can click right on the invisible border of the object. The appearance of both objects are obscured by "tool tip" badges when you veiw them in layout mode.
In some other layouts such an invisible rectangle object is what has been added to the layout and setup as a button. Such is the case on the Record Detail Contacts layout in the portal on the Related Contacts panel of the bottom tab control. On that layout, the triangle is just a graphic object, but it's located underneath the transparent rectangle that covers the entire portal row and which is set up as a button.
Part of my problem I now see was that things like rectangles must be selected by clicking on their borders rather than somewhere in the middle of the object! Never played with rectangels or circles yet.
But one followup - the "invisible" rectangles in the ECS (and there arevplenty as I look closely) in Layout mode all have a somewhat thick, fuzzy gray border, which enables me to select them. But even if I match the Inspector values in appearance when I create an invisble rectangle, I can't get that same effect, so my object completely dispappears. What is the trick to that?
Again, many thanks!
Buttons will be surrounded by a grey rectanble in FileMaker 11 and older if you enter layout mode and select View | Show | Buttons.