I'd like to be able to put a border here, connected to the tab border (in other words, I'd like to have one both above and below panel.childheader.default):

Steven created a new element for that last week:
<element id="TabsBar.BorderLine" bdr="xxx,xxx,xxx" />
But that one is not working when the tabs are in the caption bar, so for that we would need another new one:
<element id="TabsBar.TabInCaptionBar.BorderLine" bdr="xxx,xxx,xxx" />