how do I return a HIGHLIGHTED (not selected) item from a ListBox?

Private Sub CommandButton1_Click()

Dim r As Long

Range("A6").Select

r = Range("A6", Range("A6").End(xlDown)).Cells.Count

For x = 0 To r
    For i = 0 To CSJList.ListCount - 1
        'You don't have to select it to iterate the list.
        'CSJList.Selected(i) = True
                
        If CSJList.List(i).Value <> ActiveCell.Offset(x, 0).Value Then
            ActiveCell.Offset(r, 0).EntireRow.Hidden = True
        End If
    Next i
Next x
End Sub

You can do away with the combobox and only use the listbox. Set the MultiSelect=True, then the user can select multiple items in the listbox.

Private Sub CommandButton1_Click()

Dim r As Long

Range("A6").Select

r = Range("A6", Range("A6").End(xlDown)).Cells.Count

For x = 0 To r
    For i = 0 To CSJList.ListCount - 1
        If Not CSJList.Selected(i) Then
            If CSJList.List(i).Value <> ActiveCell.Offset(x, 0).Value Then
                ActiveCell.Offset(r, 0).EntireRow.Hidden = True
            End If
        End If
    Next i
Next x
End Sub