I found an undocumented feature in widget.newTabBar( ) !

tabs:deSelectAll()

will clear the currently selected tab, but now I can't set a selected tab (only works if done at creation)

I've tried

tabs.buttons[3].selected = true

but this does nothing...

Anybody know how to set a tab as selected after creation of the tab bar?

This is missing out of the current implementation, but will be added in a future widget update.