Hi,
I think you mean you are using Processor Expert for the developing of your project. Unfortunately the AsynchroSerial component which uses the UART module does not support to implement the Single-wire feature in the component settings, this is something you need to code up by yourself.
There is another good option to set this register via Processor Expert's component. Add a Init_UART component and in the Component Inspector Window of this component you are able to write to this registers, like the image below shows.

I hope this information can help you.
Regards,
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