On Linux you can create a mime type for Gui Guider so that it is possible to open a project through a file manager
For instance here is what I generated:
cat share/mime/packages/application-x-guiguider.xml
<?xml version="1.0" encoding="UTF-8"?>
<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
<mime-type type="application/x-guiguider">
<icon name="Gui-Guider"/>
<glob-deleteall/>
<glob pattern="*.guiguider"/>
</mime-type>
</mime-info>
Unfortunately, GUI guider doesn't support opening a .guiguider file through the command line