Cool, that's what i thought shipping for the first build
In addition, since i like flexibility, you will be able to place the grid listing "hidden children" either in the tab panel, at the index you want, or at any index of the main panel (so before the tabs, the content, or after).
It's also possible to hide the content field, or just display it collapsed.
This is possible either globally, or per context (using system/context setting).
Working nicely so far... my biggest problem being : find a name for that CRC! (for now : "Hidden children container")
☆ A M B ☆