How to copy/autofill to last item if below cell is blank

Hello tt3,

use below code for given task:

Option Explicit

Sub Copy_Below()
    
Dim sh As Worksheet
Dim rng As Range
Dim cell As Range

Set sh = ThisWorkbook.Sheets("Sheet1")
Set rng = sh.Range("A3:A" & sh.Cells(Rows.Count, "A").End(xlUp).Row)

For Each cell In rng
    If cell.Value = "" Then
        cell.Value = cell.Offset(-1, 0).Value
    End If
Next
End Sub

Regards,
BS