How to Command Line to Not Overwrite and "KeepBoth"

I have been using TeraCopy command line successfully for some time using the following (example) command:

TeraCopy.exe Copy C:\Users\Steve\Downloads\%steveFilename% C:\Users\Public\Documents /OverwriteAll /Close >NUL

My dilemma: I would like to copy another (different) file on occasion using the command line and I would like to utilize the option "KeepBoth" available in the interactive version. However, I don't find this option in the documentation for the command line and my initial attempts have failed.

Any help is appreciated!

Thanks,

-Steve