WindowBuilder Design Tab incomplete in Eclipse

Solution 1:

This is a known and already fixed issue when running Eclipse with Java 16 or higher:

WindowBuilder issue #45 - Reflective access with CGLIB breaks windowbuilder in java 16 and higher

Update: The issue has been fixed. It is already available in the WindowBuilder Nightly Build (update site: https://download.eclipse.org/windowbuilder/lastgoodbuild/) and will be available in the upcoming WindowBuilder 1.9.8 release.