Hi Urban - that is a good request for a feature enhancement. Currently it starts in the beginning. From what I am hearing, you would like to be able to set the range of the window on the bottom to a default starting position correct?
It is possible to sort date dimension to be descending, which will put the range slider at the latest points on your line chart, but that may not be ideal.
Let me ask around and see if there is a work-around.