-
Select Custom Curve Trim from the Draw toolbar.
-
Select curve to trim near the end to be trimmed.
-
Select the trimming object.
-
The result is a trimmed curve.
In reality the curve is not trimmed. Its display (symbology) is just overridden to display a shorter (trimmed) curve, but the original geometry is still kept in the file. When you select the trimmed curve you will also get modification handles beyond the trimmed curve:
This allows you to restore the original B-spline curve shape in case the trimming object is moved in such a way that extends the trimmed curve. If the original shape were not kept, the only available extension would be tangent segment, which would not be the proper shape.