I can see that the feature is per project but I need it on start up, anyone know what I can do? thanks!
You can make any customisations to a scene file, then save it as both new.c4d & tempate.c4d - you need to save the files to the folder that opens from preferences -> Preferences folder.
For example AppData\Roaming\Maxon\Maxon Cinema 4D 2023_BCDB4759 , you save the files in here.
So within that file, you can customise any settings you like & that will always be used for your default file.
The only exception is when importing other formats - it won’t count when you open an FBX, or an OBJ, for example. But whenever you make a Cinema 4D file, it will contain your settings.