To Extend or Shorten Multiple Elements to Their Intersection with Another Element

Select the Trim to Element tool ( Drawing > Home > Modify ).
In the tool settings window, turn on the Select cutting element first check box.
Select the cutting element.
Do one of the following:

Drag a selection line across multiple elements to extend or shorten.

or
Press <Ctrl> and select multiple elements to extend or shorten. Element selection stops when you enter a data point.

As soon as you select the element(s) to extend or shorten, they are instantly extended or shortened to their intersection with the cutting element.

Multiple elements selected and extended to a single element.