Tested with Windows 11, but should work with older Windows Versions too (Example with Umlauts for Mp3tag)

add-windows-context-menu-item.bat

goto comment
 
    /*
    |--------------------------------------------------------------------------
    | Instruction
    |--------------------------------------------------------------------------
    |
    | * With Notepadd++
    | * [For specialchars and Umlauts] `Encoding` => `Convert to ANSI`
    | * [For specialchars and Umlauts] `Language` => `M` => `MS-Dos Style`
    | * Set `FileLocation`, `ItemText and `ItemNamespace`
    | * Save file as *.bat
    | * Run file as Administrator
    |
    */
 
:comment
@echo off
 
SET "FileLocation=C:\Users\norma\OneDrive\Dokumente\Sync\Mp3tag\Mp3tag.exe"
SET "ItemText=In Mp3tag öffnen"
SET "ItemNamespace=Mp3tag"
 
echo Adding file entries
@reg add "HKEY_CLASSES_ROOT\*\shell\%ItemNamespace%" /t REG_SZ /v "" /d "%ItemText%"   /f
@reg add "HKEY_CLASSES_ROOT\*\shell\%ItemNamespace%" /t REG_EXPAND_SZ /v "Icon" /d "%FileLocation%,0" /f
@reg add "HKEY_CLASSES_ROOT\*\shell\%ItemNamespace%\command" /t REG_SZ /v "" /d "%FileLocation% \"%%1\"" /f
 
echo Adding within a folder entries
@reg add "HKEY_CLASSES_ROOT\Directory\Background\shell\%ItemNamespace%" /t REG_SZ /v "" /d "%ItemText%"   /f
@reg add "HKEY_CLASSES_ROOT\Directory\Background\shell\%ItemNamespace%" /t REG_EXPAND_SZ /v "Icon" /d "%FileLocation%,0" /f
@reg add "HKEY_CLASSES_ROOT\Directory\Background\shell\%ItemNamespace%\command" /t REG_SZ /v "" /d "%FileLocation% \"%%V\"" /f
 
echo Adding folder entries
@reg add "HKEY_CLASSES_ROOT\Directory\shell\%ItemNamespace%" /t REG_SZ /v "" /d "%ItemText%"   /f
@reg add "HKEY_CLASSES_ROOT\Directory\shell\%ItemNamespace%" /t REG_EXPAND_SZ /v "Icon" /d "%FileLocation%,0" /f
@reg add "HKEY_CLASSES_ROOT\Directory\shell\%ItemNamespace%\command" /t REG_SZ /v "" /d "%FileLocation% \"%%1\"" /f