Note: I am not affiliated with the develeopment of the Advanced GUI spigot plugin or the Web Editor!
This is a simple Desktop app for Advanced GUI (https://www.spigotmc.org/resources/advancedgui-interactive-itemframe-guis.83636/)
If you want to build this yourself you will need to add CefSharp from nuget and the Guna.UI2.dll from the Dependency folder.
When you download a GUI from the webeditor it will be saved in the Projects folder inside the Applications directory.
You licence key, and project file data / cookies will be saved at C:\Users\user\AppData\Roaming\AdvancedGUI\ ( deleting this folder will reset all your Advanced GUI data )
Preview: