Flat view Tabs (removing border)

I have left aligned my Tabs and would like to have a flat view of the Tabs, meaning with no borders between them. Is this possible?

The borders between them use the Highlight and Shadow colors from Preferences / Colors and Fonts / Directory Opus Colors / Pane borders.

Changing those will affect other borders as well, but if you make them the same as or similar to the tab background color then they'll still stand out in other places (based on how the colors are being used in your screenshot, at least).