Hmm... first of all, if you are talking about Qto_ (Quantity take-off) set then it is existing since IFC4 and only for IfcStairFlight:
There are only 3 values: Length, GrossVolume and NetVolume.
By the way, some basic values are included into Calculated Values - length in planview, width in planview, total height, surface area and volume. Problems are that there is not length by stairway and that X and Y are not Length and Width and it will provide wrong results as "length" and "width", if this stair is not going by X and especially if this stair will be rotated in the planview.
Another problem is that there are not such specific attributes in IFC - neither in Pset_StairCommon nor in Pset_StairFlightCommon, so you can't match Allplan's attribute with IFC-attribute, even if you would to do this.
It seems like only one solution is here - add User-defined attribute in Allplan and read this attribute in IFC as Allplan's attribute.