QDevelop, a new IDE for Qt4

[jlbrd]

You have a problem because you have created a project with a template "subdirs". A "subdirs" project can contains only other projects. In this kind of project, it is not possible to add files. And it is not possible to delete the main project, you can close it instead.
This behavior is the same with all platforms and is not a Linux problem.

If you want to create a classical project (without sub-projects), choose "app" to template in the Options dialog.