Does the word or phrase (e.g. the name) appear only once in the document? Bookmark names must be unique so only the last found name would be bookmarked. That might not matter if you are collating the bookmarks from the document, but if it does then it's another reason to use content controls instead. However as you appear to be selecting the text to bookmark rather than automating it, the following macro will replace the selected text with XXX and add a bookmark named from the selection (provided the selection does not contain illegal characters). The code goes in the normal template so that it applies to all documents - http://www.gmayor.com/installing_macro.htm
Option Explicit
Sub ReplaceSelectionWithBookmark()
'Graham Mayor - https://www.gmayor.com - Last updated - 27 Dec 2018
Const strBM As String = "XXX"
Dim oRng As Range
Dim strText As String
Dim i As Integer
Set oRng = Selection.Range
If Len(oRng) > 4 And Len(oRng) <= 40 Then
oRng.MoveEndWhile Chr(32), wdBackward
oRng.MoveStartWhile "0123456789"
strText = Replace(oRng.Text, Chr(32), Chr(95))
If strText = "" Then GoTo err_Handler
oRng.Text = strBM
oRng.Bookmarks.Add strText
oRng.Collapse 0
oRng.Select
Else
GoTo err_Handler
End If
Set oRng = Nothing
lbl_Exit:
Exit Sub
err_Handler:
Beep
MsgBox "Select a non-numeric text between 4 and 40 characters long."
GoTo lbl_Exit
End Sub