SlickEdit doesn't have the capability to create Xcode format projects from scratch, but can read (most) projects that are first created in Xcode. And you will still need the .xcodeproj for adding, removing, and renaming files in the project.
Right now Xcode projects are essentially a "read only" format for SlickEdit. But once you've got the project created, you can use SlickEdit for code editing, building, and debugging.