Hover over the border (I would suggest to use the full screen, i.e. maximize)

Very nice!
Maybe for the long-term future you could look into how to make better use of vertical space. Currently, there are 7 (5 in fullscreen mode)= different sections from content to top of the page. Maybe a compact mode would be nice or less space for content headlines.

Yes you can drag it in the UI :) it's a new feature in v1