Identify a value in a column and repeat it until another specific value is found

[Anonymous]

In my source data, a category of data is preceded by a title.  For example:  "MTD Waste" is followed by rows with each type of waste.  Because those waste types can also be included in different categories (i.e. quality hold), I need to be able to distinguish the category.  In excel I would do something like shown below:  =+IF(D153="MTD Winder Culls","MTD_Waste",IF(D153="Total MTD Cull:","",K152)).

I could add the column to the worksheet with the data being retrieved, but this could cause problems.  Is there a way to embed this type of logic within the query.  The solution may somehow incorporate FillDown, but I haven't figured it out.  I am at a very novice level.  

[Anonymous]

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45W8g1xUShXitWJVkoEk0lgMhlMpoDJVDAJUgcRTYQqhKqEKgWqjQUA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [col1 = _t]),
    #"Grouped Rows" = Table.Group(Source, {"col1"}, {"mtd_waste", each List.Transform([col1],(r)=>if Text.Contains([col1]{0},"w") then "MTD_Waste" else "")},GroupKind.Local,(x,y)=>Number.From(Text.Start(y[col1],3)="MTD"))
in
    #"Grouped Rows"

[Anonymous]

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45W8g1xUShXitWJVkoEk0lgMhlMpoDJVDAJUgcRTYQqhKqEKgWqjQUA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [col1 = _t]),
    #"Grouped Rows" = Table.Group(Source, {"col1"}, {{"mtd_waste", each Table.AddColumn(_, "xxx",(r)=>if Text.Contains([col1]{0},"w") then "MTD_Waste" else "")}},GroupKind.Local,(x,y)=>Number.From(Text.Start(x[col1],3)=Text.Start(y[col1],3))),
    #"Expanded mtd_waste" = Table.ExpandTableColumn(#"Grouped Rows", "mtd_waste", {"col1", "xxx"}, {"mtd_waste.col1", "mtd_waste.xxx"})
in
    #"Expanded mtd_waste"

[amitchandak]

@Anonymous ,Can you share sample data and sample output in table format?