In many skins, the vertical dividers in the header bar of the 'tracks' panel is barely noticeable.
This creates the problem that you can't see where to click and drag to adjust the width of columns.
The origin of the problem is probably that the vertical divider line draws its colour mainly from "Content[TrackDetail].Body.ListHeader" (the bottom horizontal border that is not draggable, so has no actual function) instead of from "ColumnBrowser.BottomBorderLine". (the top horizontal border that is draggable and so has an actual and similar function)
My request is to either have the divider derive its colour from the top border (Content[TrackDetail].Body.ListHeader),
or since this might create issues for old skins, probably better have a distinct element for it. (supporting gradient)