Windows 10 - Custom Protocol fails when invoked from JavaScript while it works via other methods

Question

I successfully defined into the Registry a Custom protocol (named FDMyAlbsIF). The protocol is aimed to invoke a Batch File that performs different actions depending on the received parameters.

I face two problems right now:

1. When invoking the protocol via Windows Explorer (i.e. entering into the path field the string FDMyAlbsIF:\\ AAA BBB CCC), the batch file is indeed invoked and its actions are seen (right now I just echo into a file the received command with whatever parameters are entered). When invoked from JavaScript, I get and error message that reads: Fetch API cannot load fdmyalbsif:\ "AAA" "BBB" "CCC". URL scheme "fdmyalbsif" is not supported.

2. When checking the contents of the tempo file, I see that the parameters are not passed the way I need since it is showing "fdmyalbsif:\\%20AAA%20BBB%20TTT" "" "" ""

The definitions of the protocol within the Registry are:

reg add HKEY_CLASSES_ROOT\FDMyAlbsIF /t REG_SZ /d "My Description" /f
reg add HKEY_CLASSES_ROOT\FDMyAlbsIF /v "URL Protocol" /t REG_SZ /d "" /f
reg add HKEY_CLASSES_ROOT\FDMyAlbsIF\shell /f
reg add HKEY_CLASSES_ROOT\FDMyAlbsIF\shell\open /f
reg add HKEY_CLASSES_ROOT\FDMyAlbsIF\shell\open\command /t REG_SZ /d d:\MiAlbs\Manipulate_Files.bat "%1" "%2" "%3" "%4" /f

The code I use within the JavaScript to invoke the Batch File is:

Save_Result = async () => {
                        const location = window.location.hostname;
                        const settings = {
                                            method: 'POST',
                                            headers: {
                                                        Accept: 'application/text',
                                                        'Content-Type': 'application/text',
                                                     }
                                         };
                  try {
                  const fetchResponse = await fetch(`FDMyAlbsIF:\\ "AAA" "BBB" "CCC"` , settings);
        const data = await fetchResponse.text;
        return data;
    } catch (e) {
        return e;
    }    
}
Save_Result () ;

My guess is that the use of post is inconsistent with the Custom Protocol, but I don't quite know how to phrase this request.

Edit

One more thing that may be important: When invoking the Batch File, there are some cases where one of the parameters is a multi-line string. I need this string to be received into the Batch File as-is.