Assuming each additional style is being treated exactly the same way, I would add an array of the target style names and loop it like this
Code:
Sub MarkBodyText()
' Author: A. Lockton (a/k/a Guessed) via msofficeforums.com
' Date: April 2021
' Notes: Adds "(XX)" at start of everypara styled as specified
Dim arrStyles() As String, i As Integer
arrStyles = Split("Body Text|Heading 1|Heading 2", "|") 'list of style names
Application.ScreenUpdating = False
For i = LBound(arrStyles) To UBound(arrStyles)
With ActiveDocument.Content.Find
.ClearFormatting
.Style = arrStyles(i)
Do While .Execute(Forward:=True, Format:=True) = True
With .Parent
If Left(.Text, 1) = vbCr Or Left(.Text, 1) = " " Or Left(.Text, 1) = Chr(12) Then
'do nothing
Else
.InsertBefore "(XX) "
End If
If .End = ActiveDocument.Content.End Then
Exit Do
Else
.Move Unit:=wdParagraph, Count:=1
End If
End With
Loop
End With
Next i
Application.ScreenUpdating = True
End Sub