Compatible? Yes! Well, with some caveats.
All Graffix plugins for Adobe Illustrator are functionally compatible with Adobe Illustrator CC 2019. That is, the CC 2018 version can be loaded into CC 2019 and still work. No incompatibilities have been discovered except that the new version features a scalable user interface. Graffix plugins have not yet been rebuilt to support this scaling feature, so panels, etc., will appear too small at some settings.
To use the plugins in Illustrator CC 2019, be sure you have the latest version. Download the CC 2018 version from the Graffix web site or check for updates from the About Box in each plugin from CC 2018. Place these plugins in Illustrator CC 2019’s plug-ins folder and launch. As the plugin loads, it will report that it was built for CC 2018, not CC 2019, and offer the option to “Load anyway.” Once the plugin has loaded successfully in CC 2019, it won’t ask you again.
The developer libraries for plugins built with Hot Door’s CORE libraries should be available soon, and updates will be made available soon afterward. If you have any trouble loading or using the plugins in CC 2019, please let me know and I’ll do everything I can to get you running ASAP.