This tool allows you to place a new point anywhere along a curve. Then it will split the curve on that point. This creates two separate polyline curves. The curve will be locked and the curve points will be removed.
When you select Add Point Split Curve, you will be prompted to select an existing curve.
Use the slider to move the point along the curve. You can also enter exact amounts to place the point a specific distance from the start or oend point of the curve.
The prior curve points (green in the image above) are removed as the curve is turned into two separate polylines. The new point is the end of one and the start of the other.