Modo 14.0v2 docs:

Path Falloff

The Path falloff combines the curve generator with the Path falloff. The curve generator creates a curve and the falloff reads the curve points to determine where the tool should be active. If the user has the Path falloff in the Tool Pipe at the same time as a mesh edit or Transform Tool, they may need to select the Curve Path (in Polygons mode) prior to activating the falloff. This allows you to define the curve to be used. Once the basic curve is created, you can select the tool and begin to edit. You can also click on the curve control points to edit them while the tool/falloff combination is active.

Size

This value determines the area of attenuation around the path itself, calculated as a tube around the curve's position.

Mix Mode

In instances where there are multiple falloffs applied to a transform (by using the Add option of the Falloff menu), the mix mode defines how each falloff interacts with the other.

Use World Transforms

By default, falloffs calculate their influence over transforming vertices according to their relative position, using object space vertex positions. When this option is enabled, all selected mesh surfaces are considered one surface and they deform as one.