use --allow-downgrade when starting thunderbird from command line

What would be the exact common I type for this?

In the thunderbird program directory

 .\thunderbird.exe --allow-downgrade

I tired to create a bat file in the mozilla/thunderbird directory but window10 won't allow me permission to save it, even running as administrator.

I ran the command manually from CMD in administrator mode and thunderbird started up. I then downloaded the latest version of TB and installed it. Now I am getting the message that profile is not compatible and want to create a new one.

Can you give me specific steps I need to make this work. Using the command does not seem to do anything but start Thunderbird. Help about still show the beta channel. I am running windows 10 and Thunderbird 83.0b3(64bit).