[Luxey]

Cubase has flatten function, for FX applied in audio editor mode, or whatever it is called, off line, something...

For FX inserted to the mixer's virtual rack slots, there used to be freeze function, snowflake icon, most likely it is still there, somewhere.

After functions are applied, resulting .wav files should be in the Audio pool.

However, I don't think you can convert from stereo to mono that way. Plugins that make something mono just mix both channels equally with each other to sound mono, not to be mono files.