IntelliJ IDEA 10 EAP provides two new options for Flex and FlexUnit run configurations:
Now it is very easy to select which browser or standalone Flash Player to use for running your SWF application or FlexUnit tests.
The other option allows to select if your SWF should be registered in the User Flash Player Trust directory (i.e. placed in a local-trusted sandbox). Trusted applications can interact with any other SWF files, and they can load data from both local file system and network.
Note that you can change default settings that will be applied to each newly created run configuration: see Edit Defaults button at the first screenshot.