Nextion 9 bit Communication

I want to make a 9 bit communication between nextion and stm32. stm32 has 9 bit feature but how do I configure my nextion screen for 9 bit communication

Nextion screen is always 8N1. No way to get around.

I have 2 mcu and 1 nextion screen. What would you recommend to avoid confusion?

You can make a UART hub on a separate microcontroller.