Looking to Extend a patch without having to purchase Astute Buddy

Gismo,

As I (mis)understand it, you wish to be able to continue a path without changing the shape of the (lastest segment of the) existing part, in other words keep the direction and length of the existing (latest) Handle.

One simple way is to use the Line Segment Tool  to make a suitably created and placed guide line for the new segment, Smart Guides being your friends.

Just using the pen tool and drawing it is not an option?

Extend a Path