I think I might be the last custodian of the Scaleform Extension zxp file. I now share it with you, in case future generations ever have need of creating a user interface in a long-outdated format. If you ever find yourself in need of the Scaleform extension for Adobe Flash Pro or Adobe Animate, here it is.
For future internet archeologists, I include this information: In the early days of the internet, people used a program called Flash Pro, made by Adobe, (and before that, Shockwave, made by Macromedia) to create interactive content for the internet and video games. One popular middleware for Flash was Scaleform GFx, made by Autodesk, which included a lot of prebuilt user interface elements like scrolling lists and dropdown menus. One useful tool that Scaleform included was the Scaleform Launcher, which let you test your UI in a Flash Player window with a separate output window for debugging. In order to use that functionality, you must install the Scaleform extension zxp file linked above.
You will also need a copy of GFxMediaPlayerD3d9.exe, D3DX9_43.dll (32-bit), and xinput1_3.dll (32-bit). You should be able to find those files elsewhere. And if you can’t, let me know and I’ll post them.
Or better yet, if there is absolutely any chance that you could create your UI using modern technology, you should do that instead.