I've similarly only been using the tool a few minutes, but this specific example - adding an extra row without doing any extra, manual work - seems to be eminen

I've similarly only been using the tool a few minutes, but this specific example - adding an extra row without doing any extra, manual work - seems to be eminently possible with Easel (as does automatic resizing on adding/removing rows) - the magic is Bootstrap behind the scenes, but it certainly works! Hint: try creating a page using the 'Home' template and messing with the rows/columns in the centre to get a feel for it (though it seems to work on the blank canvas, too).