Here's a Windows-based program I wrote that lets you manage the sound categories on your Spektrum NX or DX Gen2 transmitter. While you can add and edit categories on the transmitter itself (System Menu > Sound Utilities), I thought it was easier to do it on a bigger screen with a keyboard and mouse.
To use this program, simply unzip the contents of the ZIP file below. You just run the EXE file to run the program - there is nothing to install. The ZIP file includes the default categories for sound file version 1.09 in an SPM file (also below), which I made before I started the development process.
The program requires .NET Framework version 4.7.1 on your computer. That shouldn't be an issue at all on Windows 10, as the most current version is 4.8 and has been for a while. Windows 7 users might be challenged by that if you haven't updated for a couple of years. Here's a link to
download .NET 4.7.2 from Microsoft if you need to. (The download begins immediately from that page.)
The EXE file is not digitally signed, so your anti-virus software will question it the first time you run it. I'm very paranoid about security myself, so I understand you're taking a leap of faith using it. It's not a virus, and it doesn't work with any data it's not supposed to. It's written with Visual Studio for .NET 4.7. I don't know what .NET does by default for any program Visual Studio creates, but my code doesn't access the registry, the network, or any files you don't tell it to open or save.
As I created it, here's the SHA-1 Checksum for the ZIP File (version 1.0): 960a0e27c483d1446597659b049c1be8c15462c7
Documentation with screen shots is provided in the PDF file below.
DISCLAIMER: This program and the process of editing SPM model files exported from the transmitter is not supported by Horizon Hobby. Use this at your own risk.