What about selecting the current version of the opened project by default?
The problem is : if you open a gmk file, and then you want to save as a gmx file. It will display the version of the gmk file, but then you have to choose manually the version of the gmx file, or it will not work. This is not intuitive, as you don't know what version corresponds to what format. It would be much better, when you select the gmx format in the drop down list, to display only the available versions for this format. In general, let's display only the versions of the selected format.