When I create a new ActionScript project in Flash Builder, I have to add standard Flex SDK libraries manually one by one even though I have already included Flex SDK library. Am I missing some setting, so that compiler is not finding all the SWCs already present in Flex SDK library?
In Flash Builder's new Project wizard, you can create a new "Flex Project" and then select "Desktop" as the application type. In next screen, it asks for default main class, just specify your main .as (ActionScript) class file here. This way you won't have to write any MXML code and all the libraries of standard Flex library will be implicitly available for the project files.