If you look carefully at the online demos for panelTabbed in 126.96.36.199 you may notice that the tabs are sporting a slightly changed UI for situations where the number of tabs can't fit into the available horizontal space.
Here's the situation with the default representation of a tab-set when it overflows. The chevron on the right of the tab-set can be clicked to display a drop-down list of the remaining tabs.
In 188.8.131.52 we now have an alternative visualization where the hidden tabs are available on a conveyor belt and the user can scroll along the belt rather than having to use the pull-down list.
This visualization is not controlled by any property on the component but rather is switched on through the skin being used in the application. As such, all tab-sets within the application will gain the visualization if it is switched on.
To enable it you will need to create a custom skin, if you are not familiar with process then there are plenty of articles and documentation out there to help you, or you can download the demo that I've created to go along with this article. Basically I've created a custom skin that extends the new Skyros skin that 184.108.40.206 uses by default, and plugged that in to replace Skyros.
Within the skin file there is a single entry to make for panelTabbed (and a similar one for navigationPane):
And that's it, as simple as that. As I mentioned you can download a simple sample (DRM009) which shows this in action from the ADF EMG Demos Site