This is a solution how to make autocomplete drop down list with VBA :
Firstly you need to insert a combo box into the worksheet and change its properties, and then running the VBA code to enable the autocomplete.
Get into the worksheet which contains the drop down list you want it to be autocompleted.
Before inserting the Combo box, you need to enable the Developer tab in the ribbon.
a). In Excel 2010 and 2013, click File > Options. And in the Options dialog box, click Customize Ribbon in the right pane, check the Developer box, then click the OK button.
b). In Outlook 2007, click Office button > Excel Options. In the Excel Options dialog box, click Popular in the right bar, then check the Show Developer tabin the Ribbon box, and finally click the OK button.
Then click Developer > Insert > Combo Box under ActiveX Controls.
Draw the combo box in current opened worksheet and right click it. Select Properties in the right-clicking menu.
Turn off the Design Mode with clicking Developer > Design Mode.
Right click on the current opened worksheet tab and click View Code.
Make sure that the current worksheet code editor is opened, and then copy and paste the below VBA code into it.
Code borrowed from extendoffice.com
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
'Update by Extendoffice: 2018/9/21
Dim xCombox As OLEObject
Dim xStr As String
Dim xWs As Worksheet
Dim xArr
Set xWs = Application.ActiveSheet
On Error Resume Next
Set xCombox = xWs.OLEObjects("TempCombo")
With xCombox
.ListFillRange = ""
.LinkedCell = ""
.Visible = False
End With
If Target.Validation.Type = 3 Then
Target.Validation.InCellDropdown = False
Cancel = True
xStr = Target.Validation.Formula1
xStr = Right(xStr, Len(xStr) - 1)
If xStr = "" Then Exit Sub
With xCombox
.Visible = True
.Left = Target.Left
.Top = Target.Top
.Width = Target.Width + 5
.Height = Target.Height + 5
.ListFillRange = xStr
If .ListFillRange = "" Then
xArr = Split(xStr, ",")
Me.TempCombo.List = xArr
End If
.LinkedCell = Target.Address
End With
xCombox.Activate
Me.TempCombo.DropDown
End If
End Sub
Private Sub TempCombo_KeyDown(ByVal KeyCode As MSForms.ReturnInteger, ByVal Shift As Integer)
Select Case KeyCode
Case 9
Application.ActiveCell.Offset(0, 1).Activate
Case 13
Application.ActiveCell.Offset(1, 0).Activate
End Select
End Sub
Click File > Close and Return to Microsoft Excel to close the Microsoft Visual Basic for Application window.
Now, just click the cell with drop down list, you can see the drop-down list is displayed as a combo box, then type the first letter into the box, the corresponding word will be completed automatically.
Note: This VBA code is not applied to merged cells.
Source : How To Autocomplete When Typing In Excel Drop Down List?