Attached is an image that shows 3 portions of my eclipse setup. I traced a red line on section that looks to me like wasted space. A rough count of the height of these areas gives around 50 pixel rows could be recover and make better us of IMHO.
I tried to play with the Linux Theme, hoping they would be affected, but that was no help.
Unrelated by Eclipse prior to Oxygen had no option to disable the status bar at the bottom ( without also removing the tool bar at the top). Adding that opion might be a nice addition to DarkestTheme.