FlashDevelop supports editing of JSFL, but does not yet have code completion support. JSFL files are treated like JS files. You'll get syntax coloring and some token completion. Consider using the xJSFL library to help write JSFL script quicker.

• Adobe Flash CC Pro is a great JSFL editor with excellent code completion
• Haxe to compile JSFL scripts from Haxe code (Install Haxe JSFL template if wanted)