To backup your Girder install backup the following areas:

* Your GML files wherever you saved them

* Your Girder app data. This location varies depending on the
Windows version but you can find it by typing this into the
Interactive Girder Console.

print(gir.ParseString("%APPDATA%\\Promixis\\Girder \\5\\"))

backup all files in that folder and it's subfolders.

* In the registry there are 2 locations to backup.

\\HKCU\Software\Promixis\Girder\5
\\HKLM\Software\Promixis\Girder\5

If you can't find one of those don't worry as depending on the
installation it won't be there.

* The Girder installation directory.