Please see this ticket
for more info.
FDT has the option to create files such as Classes, Variables , Functions, Namespaces....but not for a generic file with an .as extension. The use case for this would be when a developer wants to use includes. While there are no plans to include a parsing of includes, we can help developers by allowing them to keep their current file structure (say if they are migrating a project from another IDE) and they can use the /FDT_IGNORE/ sytax when they refer to code in these non parsed 'Actionscript Files'.
The only catch here is that we should provide a hint to the user that the file will not be parsed. Perhaps a stub comment at the top. E.g.
// Actionscript Files are not parsed by FDT and will not provide features such as advanced code completion and error highlighting.
// References to code in these files should be surrounded with the /FDT_IGNORE/ sytax.
Another solution could be to offer some advanced code features within the include by 'faking it' as a class and the include is a class body. The catch here is that it could not refer to code within another file.