Icon Creator for the desktop

Icon Creator composes APP-6E symbols on your own machine and saves them as a single composite SVG. It covers the same symbology as the Generate page here, with the full set of amplifier controls alongside the icon and without a round trip to the server for every change.

Each download carries its own Java runtime, so there is nothing else to install - no JDK, and no JavaFX.

Pick the archive matching your system from the release page.
System File Notes
Windows ...-windows.zip 64-bit. Unzip, then run JMSFX Icon Creator.exe.
macOS ...-macos.zip Apple Silicon only Untested
Linux ...-linux.tar.gz 64-bit. Extract, then run bin/JMSFX Icon Creator.
Your browser will probably warn you

These downloads are not code signed, so Windows and macOS both treat them as coming from an unknown publisher. The warnings are about the absence of a signature, not about anything detected in the files. Signing certificates cost several hundred dollars a year, which is difficult to justify for a free tool - so the warnings are described here instead.

Windows
Chrome blocks the download as dangerous; keep it from the downloads list. Windows then shows Windows protected your PC the first time you run it - choose More info, then Run anyway. Getting past the browser does not get you past this second prompt.
macOS
Gatekeeper refuses to open the application. Right-click it in Finder and choose Open, which offers the option to run it anyway.
Linux
No warnings.
About the macOS build

The macOS download is built for Apple Silicon and will not run on an Intel Mac. Because the Java runtime is bundled, there is no fallback.

It is also untested. Nobody working on JMSFX has a Mac, so while the build is produced and checked automatically, no one has watched it run. If you try it, an issue saying whether it worked would be genuinely useful.