C# code snippet:

public override void Execute()
{
    CommandMessage commandline = application.GetCommandMessage();
    if (null == commandline)
    {
        return;
    }

    Document dsDoc = application.GetActiveDocument();
    if (null == dsDoc)
    {
        return;
    }

    Model dsModel = dsDoc.GetModel();
    if (null == dsModel)
    {
        return;
    }

    SketchManager dsSketchManager = dsModel.GetSketchManager();
    if (null == dsSketchManager)
    {
        return;
    }

    MLeader dsMLeader = dsSketchManager.InsertMLeaderWithNoneContentType( new double[] { 0.0, 0.0, 0.0, 100.0, 100.0, 0.0 }, dsMLeaderType_e.dsMLeaderType_Straight);
    if (null == dsMLeader)
    {
        commandline.PrintLine("InsertMLeaderWithNoneContentType: Failed to create MLeader");
    }

    dsMLeader = dsSketchManager.InsertMLeaderWithToleranceContentType(new double[] { 0.0, 0.0, 0.0, 150.0, 150.0, 0.0 }, "{\\Fgdt;i}vvvb{\\Fgdt;l}vv\n5\n123", dsMLeaderType_e.dsMLeaderType_Straight, dsMLeaderTolAttachmentType_e.dsMLeaderTolAttachmentType_Middle );
    if (null == dsMLeader)
    {
        commandline.PrintLine("InsertMLeaderWithToleranceContentType: Failed to create MLeader");
    }

    // Please create a block for this method
    dsMLeader = dsSketchManager.InsertMLeaderWithBlockContentType(new double[] { 0.0, 0.0, 0.0, 200.0, 200.0, 0.0 }, "<block name>", dsMLeaderType_e.dsMLeaderType_Straight);
    if (null == dsMLeader)
    {
        commandline.PrintLine("InsertMLeaderWithBlockContentType: Failed to create MLeader");
    }

    dsMLeader = dsSketchManager.InsertMLeaderWithNoteContentType(new double[] { 0.0, 0.0, 0.0, 250.0, 250.0, 0.0 }, 20.0, "MLeader with note", dsMLeaderType_e.dsMLeaderType_Straight);
    if (null == dsMLeader)
    {
        commandline.PrintLine("InsertMLeaderWithNoteContentType: Failed to create MLeader");
    }
}

For more information about MultiLeaders, see these DraftSight user-interface help > Creating and Modifying Dimensions > Working With Leaders and Geometric Tolerances topics:

• Creating MultiLeaders
• Modifying MultiLeaders
• Working with MultiLeaderStyles

IDocument::GetObjectByHandle

ISelectionManager::GetSelectedObject

ISelectionManager::GetSelectedObjects

ISketchManager::GetEntities

ISketchManager::InsertMLeaderWithBlockContentType

ISketchManager::InsertMLeaderWithNoneContentType

ISketchManager::InsertMLeaderWithNoteContentType

ISketchManager::InsertMLeaderWithToleranceContentType

MLeader