Design acceleration spectra used within the framework of design rules are automatically calculated according to the 5% damping ratio according to Codes.
If the designer want to change the damping ratio, it can be changed from response spectrum case tab.
İnternational Design Codes
ASCE 7-16 : Damping Ratio per ASCE 7-16 with ideCAD
TSC 2018 : Damping ratio (220.127.116.11)