the latest nightly build on our way towards Spring IDE 2.0 M3 contains XML editing support for Spring Web Flow flow definitions and Web Flow's 2.0 configuration namespace.
More details are available at http://springide.org/project/wiki/WebflowXmlEditor. The build can be installed from our nightly build updatesite (http://springide.org/updatesite_nightly/).
Please provide us with your thoughts and feedback on this, as we want to make the Web Flow support as valuable as possible. Comments in this thread are welcome.