How do I open a file from TextEdit on MacOSX? How do I create a link in TextEdit on MacOSX that will let me open an external application?
Doing TextField / Edition / Edit Link (Add Link if you've got any text selected)or Command+K, will let you add an Hyperlink.

Typing file:// before the application's file path will give you a bluish clickable text, which, on click, will open the file path. Here's how it should look like:

file:///Applications/NameOfTheApplication.app

It won't open the Application, but will open a new Finder window with the item already selected.