In response to a question asked, I added a paragraph labelled "GUI Design Documents" to this article.
When working with text files (.4gl, per etc), you can use the latest version of Genero Studio and edit files, and build, run, and debug applications using older versions of compiler and runner. With 4fd, 4rp files that have their own GUI Designer, to edit those files you have to use a version of Genero Studio that matches the version of those files. If you use a newer version of Studio with an older 4fd, 4rp etc file you will be warned that saving the file will upgrade the 4fd, 4rp etc file. Unfortunately Genero Studio does not have an option for the GUI Designer to only have options applicable to the version of when the 4fd, 4rp etc was created, nor does it have the ability to do a File Save As as an older version. So even though I encourage and do use latest version of Genero Studio where possible, if someone raises an issue with an older 4fd, 4rp etc then I have to open an older version of Genero Studio in order to edit that file.
Reuben