It's still not clear what you want. Perhaps:
Code:
Sub Demo()
With Selection
.Paste
With .Find
.ClearFormatting
.Replacement.ClearFormatting
.Text = "https://doi.org/"
.Replacement.Text = "doi:^c"
.Forward = True
.Wrap = wdFindContinue
.Format = False
.MatchCase = False
.MatchWholeWord = False
.MatchWildcards = False
.MatchSoundsLike = False
.MatchAllWordForms = False
.Execute Replace:=wdReplaceOne
End With
If .Find.Found = True Then
.Start = .Start + 4
.Hyperlinks.Add Anchor:=.Range, Address:="https://" & .Text, TextToDisplay:=.Text
End If
End With
End Sub