Decelerate spindle start? (E-670)

So we think the turning spindle climbs up to max rpm way too fast, and I have looked for a way to slow it down to no avail. No regular parameter controlls this afaik, and my knowledge about 1131 parameters is lacking.

Does anyone know how to do it? And - is it possible to find a list of those "hidden" parameters and what they mean? Of course the service guys refuse to provide information about it..