The Segment Parameters separator shows with many (not ALL) Traditional Motion-Laws.
The Segment-Parameters, when they show, are unique to the Motion-Law.
The best way to learn about the Segment-Parameters is to experiment with their values
Segment-Parameters of the Since-Constant-Cosine Motion-Law
The image above shows the three Segment-Parameters for the Sine-Constant-Cosine motion-law.
In this case, you can edit the Segment-Parameters to give other Traditional Motion-Laws.
For example, Commercial Indexers with a Modified Sine-Constant-Cosine motion. The Constant refers to a period of ZERO-Acceleration, to give Constant-Velocity.
A family of commercial indexers may include, within the index-period, a Constant-Velocity of 20%, 33%, 50%, or 66% of an Indexing Motion Segment.
In MotionDesigner, you can specify any percentage of Constant Velocity.
NOTE: The Constant-Fraction parameter above, refers to the Non-Zero Constant Acceleration, and not the Zero Constant-Acceleration.