Assuming the content controls to be bookmarked are all in table cells, you could use:
Code:
Sub Demo()
Application.ScreenUpdating = False
Dim CCtrl As ContentControl, Rng As Range
For Each CCtrl In ActiveDocument.ContentControls
With CCtrl
If .Range.Information(wdWithInTable) = True Then
Set Rng = .Range.Cells(1).Range
With Rng
.End = .End - 1
.Bookmarks.Add CCtrl.Title, Rng
End With
End If
End With
Next
Application.ScreenUpdating = True
End Sub