You can then browse into Line Ends and create a new pattern:
Make sure that the pattern is scaled, and select the type of line-end behaviour:
Finally, you can create your pattern. This is where things get a little odd. I’ve found the best behaviour occurs when you make your pattern extremely small – most of my patterns are about 4mm x 2mm. You might have some difficulty with line end orientation.
You can now use it as a line end in any normal Visio line dialog.