UI toolkit version / used in JEB versions:

4.19    used by JEB 4 latest
4.20    not used by JEB
4.21    not used by JEB
4.22    not used by JEB
4.23    not used by JEB
4.24    not used by JEB
4.25    not used by JEB
4.25    not used by JEB
4.27    not used by JEB
4.28    used by JEB 5.0 to 5.2
4.29    used by JEB 5.3 to 5.5
4.30    used by JEB 5.6 to 5.10
4.31    used by JEB 5.11+

How to downgrade your UI toolkit:
- navigate to the folder of the UI toolkit you wish to downgrade JEB to
- download jface.jar
- download the swt.jar file that matches the your system
- drop them in the JEB/bin/app/ folder (overwrite the existing files)