Rem 1) select the text lines representing a table whose columns are separated by the tab character
Rem 2) run this macro
Rem 3) result: the tab characters are replaced by two or more space characters such a way each column
Rem    has the same number of characters
Rem 4) you may then copy/paste those text lines inside HTML <pre>...</pre> it will look like a table
Sub tabs_to_spaces()
    Dim par As Paragraph
    Dim pars() As Paragraph
    Dim arr(50) As Integer ' 50 tabs maximum per line

    Application.ScreenUpdating = False

    max_ztab = -1
    For Each par In Selection.Paragraphs
        old_x = 1
        ztab = LBound(arr)
        Do While old_x <> 0
            x = InStr(old_x, par.Range.Text, Chr(9))
            If x = 0 Then
                zlen = Len(par.Range.Text) - old_x + 1
            Else
                zlen = x - old_x
            End If
            If zlen > arr(ztab) Then arr(ztab) = zlen
            If ztab > max_ztab Then max_ztab = ztab
            ztab = ztab + 1
            If x = 0 Then
                Exit Do
            Else
                old_x = x + 1
            End If
        Loop
    Next

    ReDim pars(Selection.Paragraphs.Count)
    For i = 1 To Selection.Paragraphs.Count
        Set pars(i) = Selection.Paragraphs(i)
    Next

    For i = 1 To UBound(pars)
        Set par = pars(i)
        old_x = 1
        ztab = LBound(arr)
        Do
            x = InStr(old_x, par.Range.Text, Chr(9))
            If x = 0 Then
                Exit Do
            End If
            Call par.Range.Characters(x).Delete
            zlen = arr(ztab) - (x - old_x) + 2 ' + 2 spaces between each column
            ztab = ztab + 1
            Call par.Range.Characters(x).InsertBefore(Space(zlen))
            old_x = x + zlen
        Loop
    Next

    Application.ScreenUpdating = True

End Sub

Sub tabs_to_markdown()
    Dim par As Paragraph
    Dim pars() As Paragraph
    Dim arr(50) As Integer ' 50 tabs maximum per line

    Application.ScreenUpdating = False

    ' calculate array "arr" containing column widths, and max_ztab
    max_ztab = -1
    For Each par In Selection.Paragraphs
        old_x = 1
        ztab = LBound(arr)
        Do While old_x <> 0
            x = InStr(old_x, par.Range.Text, Chr(9))
            If x = 0 Then
                zlen = Len(par.Range.Text) - old_x + 1
            Else
                zlen = x - old_x
            End If
            If zlen > arr(ztab) Then arr(ztab) = zlen
            If ztab > max_ztab Then max_ztab = ztab
            ztab = ztab + 1
            If x = 0 Then
                Exit Do
            Else
                old_x = x + 1
            End If
        Loop
    Next

    ReDim pars(Selection.Paragraphs.Count)
    For i = 1 To Selection.Paragraphs.Count
        Set pars(i) = Selection.Paragraphs(i)
    Next

    For i = 1 To UBound(pars) ' CAUTION must be 1, not lbound(pars)
        Set par = pars(i)
        Call par.Range.InsertBefore("| ")
        old_x = 1 + Len("| ")
        ztab = LBound(arr)
        While old_x < par.Range.Characters.Count
            ' get the position of the next TAB character
            x = InStr(old_x, par.Range.Text, Chr(9))
            If x <> 0 Then
                ' delete the TAB character
                Call par.Range.Characters(x).Delete
            Else
                x = par.Range.Characters.Count
            End If
            ' insert
            column_right = Space(arr(ztab) - (x - old_x) + 1) + "| "
            Call par.Range.Characters(x).InsertBefore(column_right)
            old_x = x + Len(column_right)
            ' next column
            ztab = ztab + 1
        Wend
    Next

    Application.ScreenUpdating = True

End Sub