Group By & logic for historical view

read about GroupKind.Local

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("ddAxCoQwEEbhq0hqQTNJTNIvtttsJ97A1vu7oJJo5lVTfAz8vGUxdhLTm3nftv+xdrCDjCJm7d8kTKe4VgTFoXiUgDKhRJSEklHsyMQVLvHYRxGH4lFCK12JozxElISSW/l9P7mKo5GS4CalwU2nBOx2SUzl5zm8ltxK166uP16rHyRMuK2sXg8=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Store = _t, #"Support Type" = _t, #"Reporting Month" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Reporting Month", type date}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"Store", "Support Type"}, {{"Start Date", each List.Min([Reporting Month]), type nullable date}, {"End Date", each List.Max([Reporting Month]), type nullable date}},GroupKind.Local),
    #"Filtered Rows" = Table.SelectRows(#"Grouped Rows", each ([Support Type] <> " "))
in
    #"Filtered Rows"

How to use this code: Create a new Blank Query. Click on "Advanced Editor". Replace the code in the window with the code provided here. Click "Done". Once you examined the code, replace the entire Source step with your own source.