insert a blank row conditionally in PQ

Here try this:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WSlTSUTIEYkulWJ1opSQgywiILcC84tIk3ZL8ksQcoIgxEJuDRZOBLBMgNsNQYwrGINEUsDxIHYiXCtYLMgNdhwXYdpAoTMQSIhILAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [col1 = _t, index = _t, value = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"col1", type text}, {"index", Int64.Type}, {"value", Int64.Type}}),
    #"Added Custom" = Table.AddColumn(#"Changed Type", "Custom", each if [col1] = "sub-total" then "1"&Text.Repeat(" @1",1) else [col1]),
    #"Merged Columns" = Table.CombineColumns(Table.TransformColumnTypes(#"Added Custom", {{"index", type text}, {"value", type text}}, "en-US"),{"col1", "index", "value"},Combiner.CombineTextByDelimiter(":", QuoteStyle.None),"Merged"),
    #"Split Column by Delimiter" = Table.ExpandListColumn(Table.TransformColumns(#"Merged Columns", {{"Custom", Splitter.SplitTextByDelimiter(" ", QuoteStyle.Csv), let itemType = (type nullable text) meta [Serialized.Text = true] in type {itemType}}}), "Custom"),
    #"Added Custom1" = Table.AddColumn(#"Split Column by Delimiter", "Custom.1", each if[Custom] ="@1" then null else [Merged]),
    #"Removed Columns" = Table.RemoveColumns(#"Added Custom1",{"Merged", "Custom"}),
    #"Split Column by Delimiter1" = Table.SplitColumn(#"Removed Columns", "Custom.1", Splitter.SplitTextByDelimiter(":", QuoteStyle.Csv), {"Custom.1.1", "Custom.1.2", "Custom.1.3"}),
    #"Changed Type1" = Table.TransformColumnTypes(#"Split Column by Delimiter1",{{"Custom.1.1", type text}, {"Custom.1.2", Int64.Type}, {"Custom.1.3", Int64.Type}}),
    #"Replaced Value" = Table.ReplaceValue(#"Changed Type1",null,"",Replacer.ReplaceValue,{"Custom.1.1", "Custom.1.2", "Custom.1.3"}),
    #"Renamed Columns" = Table.RenameColumns(#"Replaced Value",{{"Custom.1.1", "col1"}, {"Custom.1.2", "Index"}, {"Custom.1.3", "Value"}})
in
    #"Renamed Columns"

Outcome like this: