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SUMMARY
As a user, when I install KDiff3 using the Appx Sideload App, I would like to use KDiff3 on the command line. This is especially important when I want to use it as a diff or merge toll with Git for Windows. It is also important in the environment of a company Windows PC where it is forbidden by policy to install applications normally and the only option is using sideloaded apps or the Windows App Store.

The kdiff3.exe binary installed via sideloaded apps cannot be executed via command line. This is forbidden by the Windows OS. You can use a special command using explorer.exe shell:<Application path+family ID>!<AppID> but command line arguments don't work. And this solution doesn't work in GitBash either.

STEPS TO REPRODUCE
1. Double-click KDiff APPX file provided in the binary downlaods.
2. Open command line/powershell/gitbash
3. Type kdiff3.exe <command line args>

OBSERVED RESULT
Command is not recognized.

EXPECTED RESULT
KDiff3 application starts in diff or merge mode according to command line arguments

SOFTWARE/OS VERSIONS
Windows: 

ADDITIONAL INFORMATION
I think there is missing information in the AppxManifest.xml that could automatically create the necessary aliases to use KDiff3.exe in the command line properly upon installation.

Please see the following as it might help you implement the fix:
https://learn.microsoft.com/en-us/uwp/schemas/appxpackage/uapmanifestschema/element-uap5-appexecutionalias
https://www.advancedinstaller.com/user-guide/win-store-app-execution-alias-props.html