Custom column with filter on Min value

Hi Fab117 ,

You can try this:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjQyVtJRyivNyVGK1YFxjZDYpkhsNGVoXHMktjES2xCbFhNTMyDXBImNJmWEW8ociW2hFBsLAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [ProjectId = _t, MilestoneNumberNotCompleted = _t]),
    #"Grouped Rows" = Table.Group(Source, {"ProjectId"}, {{"AllRows", each _, type table [ProjectId=nullable text, MilestoneNumberNotCompleted=nullable text]}}),
    #"Add Current Milestone" = Table.TransformColumns(
        #"Grouped Rows",
        {
            {"AllRows", each 
            
            Table.AddColumn(
                _,
                "CurrentMilestone", 
                (r)=> if r[MilestoneNumberNotCompleted] = List.Min(_[MilestoneNumberNotCompleted]) 
                    then r[MilestoneNumberNotCompleted] else null 
                ,type text
                )
            }
        }
    ),
    Expanded = Table.Combine(#"Add Current Milestone"[AllRows])
in
    Expanded