Modify library items

Question

In Illustrator CS4, can permanent changes be made to built-in graphic styles, like arrowheads? We want to modify the shape of an arrowhead built into the Effects-Stylize menu for future usage.

Answer 1

Illustrator's Arrowhead feature is about 20 years behind corresponding features in other drawing programs. Most programs let you customize the arrowheads using any vector artwork you draw. Given AI's Symbols, one would expect to be able to simply and straightforwardly asign any Symbol as an arrowhead.
That would be one approach to the long-needed improvement. Better, though, would be something I have been proposing for years: a couple of carefully-thought out enhancements to the Brushes feature set.
The problems with the current behaviors of Pattern Brushes are:
* The end tiles ordinarily "wedge" distort with the shape of the path, as do the side tiles. This should be optional. The completely unintuitive workaround for this is to set the art of end tile outboard of the invisible rectangle that defines its area.
* The corner tiles of Pattern Brushes meanwhile are incapable of wedging--so the usefullness of that sub-feature is limited for corner points at which the adjacent segments join at angles other than right angles.
* Pattern Brushes require content to exist in their side tile. I see no reason for this necessity.
I would like to see these enhancements:
* All four Brush types should be given optional End Tiles. The End Tiles shojuld have an option to disallow distortion. The End Tiles should have an independent option for orientation relative to the path or the page.
* Art Brushes, Pattern Brushes, and Scatter Brushes should have an option to disallow scaling of strokes contained in the Brush artwork. (Symbols should also provide this option.)
* A collection of Brushes set up to emulate the traditional arrowhead styles should be included with the default installation.
Those changes would obviate the very archaic Arrowheads feature. I understand that it is probably kept around for backward compatability with files created in legacy versions. But if such a fundamental feature is never going to be updated, it needs to go. Adobe's practice of continually adding features, but seldom fleshing them out, makes Illustrator increasingly cluttered with long-outdated legacy features and never-quite-satisfying new features.
All that said (again), you can use Brushes in combination with the ability to assign multiple strokes to a single path to achieve the kinds of arrowheads you have described (and much more):
A PDF describing the technique in detail is here.
JET