Редактирование двух связанных ComboBox

Public Class Form1
    Dim idxCurItem As Integer
    Dim tSourceList1() As String = {"Title_1", "Title_2", "Title_3", "Title_4", "Title_5"}
    Dim tSourceList2() As String = {"CommandLine_1", "CommandLine_2", "CommandLine_3", "CommandLine_4", "CommandLine_5"}
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        cboTitle.DropDownStyle = 0
        cboTitle.Height = 100
        cboCommandLine.DropDownStyle = 1
        cboTitle.Items.AddRange(tSourceList1)
        cboCommandLine.Items.AddRange(tSourceList2)
        idxCurItem = 0
        cboTitle.SelectedIndex = 0 'становимся на первую строку списка
        cboCommandLine.SelectedIndex = 0 'становимся на первую строку списка
    End Sub
    Private Sub cboTitle_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cboTitle.SelectedIndexChanged
        idxCurItem = cboTitle.SelectedIndex
        cboCommandLine.SelectedIndex = idxCurItem
    End Sub
    Private Sub cboTitle_TextUpdate(ByVal sender As Object, ByVal e As System.EventArgs) Handles cboTitle.TextUpdate
        If idxCurItem >= 0 Then
            cboTitle.Items(idxCurItem) = cboTitle.Text
        End If
    End Sub
 
    Private Sub cboCommandLine_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles cboCommandLine.SelectedIndexChanged
        idxCurItem = cboCommandLine.SelectedIndex
        cboTitle.SelectedIndex = idxCurItem
    End Sub
    Private Sub cboCommandLine_TextUpdate(ByVal sender As Object, ByVal e As System.EventArgs) Handles cboCommandLine.TextUpdate
        If idxCurItem >= 0 Then
            cboCommandLine.Items(idxCurItem) = cboCommandLine.Text
        End If
    End Sub
End Class

    Dim index As Integer = 0
    Private Sub cboTitle_TextUpdate(ByVal sender As Object, ByVal e As System.EventArgs) Handles cboTitle.TextUpdate
        index = cboTitle.SelectionStart
        If idxCurItem >= 0 Then
            cboTitle.Items(idxCurItem) = cboTitle.Text
            cboTitle.SelectionStart = index
        End If
    End Sub

Dim index As Integer = 0
Dim iSelLen As Integer = 0
Private Sub cboTitle_TextUpdate(ByVal sender As Object, ByVal e As System.EventArgs) Handles cboTitle.TextUpdate
        index = cboTitle.SelectionStart
        iSelLen = cboTitle.SelectionLength
        If idxCurItem >= 0 Then
            cboTitle.Items(idxCurItem) = cboTitle.Text
            cboTitle.SelectionStart = index
            cboTitle.SelectionLength = iSelLen
        End If
End Sub

Dim str1() As String = {"aa", "bb", "cc", "dd", "ee"}
insertToArray1(2, "zz", str1)
Dim str2() As String = {"aa", "bb", "cc", "dd", "ee"}
insertToArray1(2, "zz", str2)
MsgBox(String.Join(", ", str1) & vbCrLf & String.Join(", ", str2))
 
Private Sub insertToArray1(ByVal ind As Integer, ByVal newStr As String, ByRef ar() As String)
    If ind < ar.Length Then
        Dim lst = ar.ToList
        lst.Insert(ind, newStr)
        ar = lst.ToArray
    End If
End Sub
Private Sub insertToArray2(ByVal ind As Integer, ByVal newStr As String, ByRef ar() As String)
    If ind < ar.Length Then
        ReDim Preserve ar(ar.Length)
        For i = ar.Length - 2 To ind Step -1
            ar(i + 1) = ar(i)
        Next
        ar(ind) = newStr
    End If
End Sub

Private Sub ComboBox1_KeyDown(sender As System.Object, e As System.Windows.Forms.KeyEventArgs) Handles ComboBox1.KeyDown
    If e.KeyCode = Keys.Enter Then
        ComboBox1.Items.Add(ComboBox1.Text)
    End If
End Sub