The -Dsun.java2d.uiScale=2.0 Java VM property can be set in Tools->Tool Properties under the General / General category to force scaling of the user interface, typically useful when using HiDPI monitors. Problem is that Java will scale the content partially, leaving 75% empty:
The fix is to open the ~/.dbvis/user.vmoptions file in a text editor and add the following
-Dsun.java2d.uiScale=2.0 -Dsun.java2d.xrender=true
Save the file and restart DbVisualizer.