Compact visualization option
One of the things I like about physical story boards is that they're more compact visually because the increment lines are not forced to be strictly a horizontal line. They can be drawn between the subtasks with vertical connectors between each column, eliminating the need for all the empty space created when columns have an uneven number of subtasks in the columns. As a first increment, you could create that option just for visualization purposes in the JPG export and see what people think of it. Ideally it would be an available view in the working space. I'd be happy to provide a visual/picture if there is a way for me to submit it.