How to convert part of array column to text, separated by commas?

Change references where required.

Sub Maybe()
Dim arr1, i As Long, a As String
arr1 = Range("A1:B" & Cells(Rows.Count, 1).End(xlUp).Row).Value
    For i = LBound(arr1) To UBound(arr1)
        If a = "" Then
            a = arr1(i, 2)
                Else
            a = a & ", " & arr1(i, 2)
        End If
    Next i
Cells(1, 4).Value = a
End Sub

Thank you.
I also found this way:

Dim arrData()
arrData = tbl.Data

nRows = UBound(arrData, 1)

Dim arr() As Variant
ReDim arr(1 To nRows - 1)

For i = 2 To nRows
     arr(i - 1) = arrData(i, 2)
Next i

Dim joinedString As String
joinedString = Join(arr, ", ")

ThisWorkbook.Sheets("Sheet2").Range("B5").Value = joinedString

Whichever code is best for you that works. Keep in mind future adaptations and maintenance.
You can shorten your code slightly.

Sub Maybe_So()
Dim arrData(), arr1, i As Long
arrData = tbl.Data
ReDim arr1(1 To UBound(arrData) - 1)
    For i = 2 To UBound(arrData)
        arr1(i - 1) = arrData(i, 2)
    Next i
ThisWorkbook.Sheets("Sheet2").Range("B5") = Join(arr1, ", ")
End Sub

Good luck

Thank you. Optimized code also works. And yes, I'd better put that in separate method and comment well.