Assuming this is a polyline dataset, multiple ways to do this. One way I can think of:

• Densifier to add point every 12 meter.
• Chopper to create segments of 12 meter.
• CoordinateExtractor to find _z_begin and _z_end.
• AttributeCreator to calculate slope based on _z_begin and _z_end.

coordinate extractor gives the z value for the splitted lines. may I know how I can differentiate z_begin and z_end ?

Multiple ways to do this, easiest is to use 2 CoordinateExtractors with mode = specify coordinate, coordinate index 0 is first point, index -1 is last point.