It would be interesting to have scrollable containers where we could add several widgets and move them through a scroll bar.
Another interesting option would be to be able to add widgets with Button, Entry, Label, inside the ListItem ou TreeItem, If this would add too much overhead perhaps scrollable widgets like List or Tree could have events like "OnScroll" and their children "ListItem" and "TreeItem" could have a "getRect" method which would return the x and y position and the width and height of the item, so we could manually create and update the widgets.