Welcome to the world of FileMaker the answer is no. FileMaker does support support IDE's or text based scripting remember it's a program for people that are't programmers and as such will have NONE of the tools that you are used in language based development environments. You can copy and paste script steps between scripts and you can write expressions or formulas in a text editor and then paste then in but you can't "code" ie make scripts outside of the scriptmaker environment.
I presume that pixi is refering to Clip Manager by fmButler, which can display the XML format FileMaker stores in the clipboard when you copy various FileMaker objects. I've found it useful for find/replace operations and for saving commonly-used snippets, but I wouldn't want to use it as a primary code editor. FileMaker developers do frequently use text editors for working with calculations, and facilitate switching between FileMaker and their text editors of choice with tools like QuickCursor; but there isn't an easy way to do the same thing with scripts. Hypothetically, it might be possible to build a cross compiler between a text-based programming language and the FileMaker XML clipboard format, but I don't know of anyone who's built it yet.