For the Stöckli HH dehydrator Dörrex with product ID 0076.71M, up to 6 additional metal grids can be used, as the appliance is equipped with 3 metal grids as standard and can be extended.

The instructions say on page 12: "Up to 10 sieves can be used".
And a little further down: "If 5 or more dehydrating trays are used, we recommend rearranging the trays."

The instructions refer to 0076 (with timer) and 0075 (without timer), to the versions with metal and plastic grids.