This new feature is the updated easy to use drag and drop navigation for editing portfolio pages.
Currently you have a set of tabs which run horizontally across the screen with icons depicting elements which you can use in your portfolio page. There is then a quite small area below where you drag those icons.
This has proved to be a little confusing at times, especially users who are working in Internet Explorer or those who have smaller screen resolutions.
The new interface condenses the elements into more readable text rather than icons for quicker navigation and a larger working area to the right of the menu.
This is how the new portfolio page editing will look like:
As you can see from the image above, the design is a lot easier to read and hopefully in a more sensible area to work with.
If you wish to get a head start with some of the changes and what they mean to you, here is a link to Mahara's support pages of the new version.