A pair of buttons for [QTTabBar](http://qttabbar.wikidot.com/) to navigate between folders within one common parent folder.

Next.QTTabBarCommand

<?xml version="1.0" encoding="utf-8"?>
<CommandButtonInfo>
  <MetaData>
    <DateCreated>2016-03-24T15:45:16.0981452+03:00</DateCreated>
    <Author>MXI</Author>
    <Contact>http://mxii.eu.org/</Contact>
    <Description>Navigate to the next folder within common parent folder.</Description>
    <Version>1.0</Version>
  </MetaData>
  <CommandButton Type="File" SubType="Normal" PersistentID="20753363">
    <FileAction>Default</FileAction>
    <DisplayText>Next</DisplayText>
    <IconResource>"%SystemRoot%\system32\SHELL32.dll", 247</IconResource>
    <IDL>14001F50E04FD020EA3A6910A2D808002B30309D19002F433A5C0000000000000000000000000000000000000056003100000000004D485B7B100057696E646F777300400009000400EFBE1643886C4D485B7B2E000000C5F9030000000200000000000000000000000000000021959900570069006E0064006F0077007300000016005A0031000000000067483A87110053797374656D33320000420009000400EFBE1643896C67483A872E000000DF010400000002000000000000000000000000000000B84C2C00530079007300740065006D00330032000000180062003200006C02005D453C122000637363726970742E65786500480009000400EFBE6246C4A96246C4A92E000000BC4E060000000100000000003D00000000000000000066D8800063007300630072006900700074002E0065007800650000001A000000</IDL>
    <Path>%SystemRoot%\System32\cscript.exe</Path>
    <Args>
      <Item>"C:\THE\PATH\TO\QtTabBar_next_prev_folder.js" next</Item>
    </Args>
    <ResolutionTimeout>5000</ResolutionTimeout>
    <MaxReturnValueWait>0</MaxReturnValueWait>
    <Options>0000000000010000000000010300</Options>
  </CommandButton>
</CommandButtonInfo>

Prev.QTTabBarCommand

<?xml version="1.0" encoding="utf-8"?>
<CommandButtonInfo>
  <MetaData>
    <DateCreated>2016-03-24T15:45:12.1444726+03:00</DateCreated>
    <Author>MXI</Author>
    <Contact>http://mxii.eu.org/</Contact>
    <Description>Navigate to the previous folder within common parent folder.</Description>
    <Version>1.0</Version>
  </MetaData>
  <CommandButton Type="File" SubType="Normal" PersistentID="20807935">
    <FileAction>Default</FileAction>
    <DisplayText>Prev</DisplayText>
    <IconResource>"%SystemRoot%\system32\SHELL32.dll", 246</IconResource>
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
    <Path>%SystemRoot%\System32\cscript.exe</Path>
    <Args>
      <Item>"C:\THE\PATH\TO\QtTabBar_next_prev_folder.js" prev</Item>
    </Args>
    <ResolutionTimeout>5000</ResolutionTimeout>
    <MaxReturnValueWait>0</MaxReturnValueWait>
    <Options>0000000000010000000000010300</Options>
  </CommandButton>
</CommandButtonInfo>

QtTabBar_next_prev_folder.js

var qs = new ActiveXObject( "QTTabBarLib.Scripting" );
var wnd = qs.activewindow;
if ( wnd )
{
    // argument value "next" or no arguments - move to next folders
    // argument value "prev" or any other    - move to previous folder
    var lookingForNext = WScript.Arguments.Unnamed.length == 0 || WScript.Arguments.Unnamed(0) == "next";
    
    var activeTab = wnd.ActiveTab;
    var currentPath = activeTab.Path;
    var fso = new ActiveXObject( "Scripting.FileSystemObject" );
    var currentFolderObject = fso.GetFolder(currentPath);
    var availablePaths = new Array();
    var currentIndex = -1;
    var i = -1;
    if ( currentFolderObject.IsRootFolder ) // enumerating drives
    {
        var currentDrive = currentFolderObject.Drive;
        var enumerator = new Enumerator(fso.Drives);
        for(; !enumerator.atEnd(); enumerator.moveNext())
        {
            var driveObject = enumerator.item();
            i++;
            availablePaths[i] = driveObject.Path;
            if(driveObject.Path == currentDrive)
            {
                currentIndex = i;
            }
        }
    }
    else // enumerating neighbour folders
    {
        var enumerator = new Enumerator(currentFolderObject.ParentFolder.SubFolders);
        for( ; !enumerator.atEnd(); enumerator.moveNext() )
        {
            var subFolder = enumerator.item();
            if(
                !(subFolder.attributes & 4)       // ignore system folders
                && !(subFolder.attributes & 1024) // ignore links or shortcuts
                //&& !(subFolder.attributes & 2)  // ignore hidden folders if needed
                )
            {
                i++;
                availablePaths[i] = subFolder.Path;
            }
            if( subFolder.Path == currentFolderObject.Path )
            {
                currentIndex = i;
            }
        }
    }
    if ( currentIndex >= 0 ) // path found
    {
        var step = lookingForNext ? 1 : -1;
        var newIndex = (availablePaths.length + currentIndex + step) % availablePaths.length;
        activeTab.NavigateTo(availablePaths[newIndex]);
    }
}