Creating a LINK_MODEL_BASED signal called FREE_MOMENT is a more general way to reference an external Force.

The segment combo box identifies the segment to which external forces have been assigned.

This allows the user to define the segment rather than the Force Platform, thus eliminating the need to make notes as to which segment is in contact with which platform.

The image above computes a signal for each contact of the Left Foot segment with any force platform. The signal shown is normalized by the default scaling factor of the Body Weight.