There are a couple of other threads on here that show how to do this,
DeadlineRepository10\plugins\Cinema4D\Cinema4D.param
edit this file and copy paste R19 details
[C4D_19_RenderExecutable]
Label=C4D 19 Executable
Category=Render Executables
CategoryOrder=0
Index=10
Type=multilinemultifilename
Default=C:\Program Files\MAXON\CINEMA 4D R19\Commandline.exe;/Applications/MAXON/CINEMA 4D R19/Commandline.app/Contents/MacOS/Commandline;C:\Program Files\Maxon\CINEMA 4D R19\CINEMA 4D 64 Bit.exe;C:\Program Files\Maxon\CINEMA 4D R19\CINEMA 4D.exe;C:\Program Files (x86)\Maxon\CINEMA 4D R19\CINEMA 4D.exe;/Applications/MAXON/CINEMA 4D R19/CINEMA 4D.app/Contents/MacOS/CINEMA 4D;/opt/maxon/cinema4d/19.000/bin/c4d_clr
Description=The path to the Cinema 4D executable file used for rendering. Enter alternative paths on separate lines.
and edit to R20
[C4D_20_RenderExecutable]
Label=C4D 20 Executable
Category=Render Executables
CategoryOrder=0
Index=11
Type=multilinemultifilename
Default=C:\Program Files\MAXON\CINEMA 4D R20\Commandline.exe;/Applications/MAXON/CINEMA 4D R20/Commandline.app/Contents/MacOS/Commandline;C:\Program Files\Maxon\CINEMA 4D R20\CINEMA 4D 64 Bit.exe;C:\Program Files\Maxon\CINEMA 4D R20\CINEMA 4D.exe;C:\Program Files (x86)\Maxon\CINEMA 4D R20\CINEMA 4D.exe;/Applications/MAXON/CINEMA 4D R20/CINEMA 4D.app/Contents/MacOS/CINEMA 4D;/opt/maxon/cinema4d/20.000/bin/c4d_clr
Description=The path to the Cinema 4D executable file used for rendering. Enter alternative paths on separate lines.
Think there’s some other bits also but no guarantee it will work as Maxon re-wrote a lot of C4D
(edit) I just tried this on a simple scene and it works for me, you may want to update the batch plugin too.