There is a StyleEditor component available in the sources, but it is partially broken due to the countless changes the library has undergone and requires a major revamp.

There are a few things I want to do:

• Move it to a separate style-editor module as it is not really needed in the core library and only takes time from L&F loading due to it's extra heavy styles [ Modules, Dependencies and Versioning #336 ]
• Revamp the editor to support recent changes and additions
• Improve editor usability to make it usable as a test application for editing default or custom styles that user can load into it

This editor is also a good showcase of what WebLaF is capable of so I'm planning to revive it in one of the upcoming updates, probably in v1.2.12.