The program allows the engineer to specify a user-specified seismic load case in the Seismic Story Forces dialog Regarding semirigid diaphragms, force, a direction angle, and eccentricities are needed to be entered (coordinates X and Y are not considered for semirigid diaphragms. they are only applicable for rigid diaphragms.

Note that eccentricity definitions (e_x, e_y) are measured from diaphragm mass center and they are defined along X and Y directions, respectively:

User Specified Seismic Loads for Semirigid Diaphragms