All of our products are supported in macOS Mojave. We have done our own beta testing using the developer builds and are not aware of any issues. Of course it's possible we missed something, so if you see any unexpected behaviour please let us know via our support form.
We always recommend to reinstall our latest version after updating macOS. Our most recent update is September 24th 2018, so please reinstall if your version is older than this. Also please make sure you are using the latest version of FCP X before updating (currently 10.4.3)
Remember to please check the vendors of any other plugins you use and hardware devices which may need drivers such as video i/o devices, raid arrays, audio interfaces etc. It is highly recommended not to update to Mojave until you have made sure all vendors have compatible versions available.
FCP.CO has an article with some more recommendations for the update process on production FCP X systems.