Makes no sense to have 0db at the centre of the fader scale as you don’t get a lot of range to balance your individual tracks. Assuming your loudest part is peaking at -6db, everything else is going to be below that leaving much less travel on your fader position.
Hi @greenfly and welcome to the community. The 0dB you are referring to is an arbitrary figure in which you can increase by 12dB and reduce by 96dB. Maybe you are getting confused with actual dB value which Scaler 3 does not offer for now (we have plans to improve this in the future).
0dB as the centre value for a fader is common practice amongst all dBFS based digital workstations.