Mapping a value based on list sequence

Hi Anonymous 

Here is my solution. Hope it helps. 

let
    Source = data,
    #"Added Custom" = Table.AddColumn(Source, "RouteSplit", each Text.Split([Route], "/")),
    #"Added Custom1" = Table.AddColumn(#"Added Custom", "Types", each List.Transform([RouteSplit], each Text.BeforeDelimiter(_, "_"))),
    #"Added Custom2" = Table.AddColumn(#"Added Custom1", "New Types", each 
        if List.Contains([Types], "GR.A FM") 
        then List.Transform([Types], each if _ = "GR" then "GR LM" else _) 
        else 
            let 
                _firstGR = List.PositionOf([Types], "GR") 
            in 
                if _firstGR = -1 
                then [Types] 
                else List.ReplaceValue(List.ReplaceRange([Types], _firstGR, 1, {"GR FM"}), "GR", "GR LM", Replacer.ReplaceValue)),
    #"Added Custom3" = Table.AddColumn(#"Added Custom2", "Route Mapped", each Text.Combine(List.Transform(List.Zip({[New Types],List.Transform([RouteSplit], each Text.AfterDelimiter(_, "_"))}), each Text.Combine(_, "_")), "/")),
    #"Removed Other Columns" = Table.SelectColumns(#"Added Custom3",{"Index", "Route", "Route Mapped"})
in
    #"Removed Other Columns"

Best Regards,
Community Support Team _ Jing
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