Thank you for your post!
The Tooltip for the Button Bar object itself does work separately of the Tooltip on the individual Segments. To test this I followed these steps:
1. Created "test.fmp12"
2. Created Button Bar w/ Three Segments
3. Set tooltip for the Button Bar Object to "Test Tooltip"
4. Set tooltip for the Segments as "Seg1", "Seg2", and "Seg3"
5. Set the Line Border on the Button Bar Object to "4"
When tested the Segments all have their own Tooltips and hovering over the Border displays the Tooltip for the Button Bar Object.
OOPS! You are correct.
The football was there. My kicking skills were off. (I should have tested with more than a 1 px. border)
Thanks for the correction.