How to normalize irregular CSV files...

Here's one way to do this in Power Query:

let

//change next line to reflect actual data source
    Source = Excel.CurrentWorkbook(){[Name="Table28"]}[Content],
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Column1", type text}}),

//remove blank rows
    #"Filtered Rows" = Table.SelectRows(#"Changed Type", each [Column1] <> null and [Column1] <> " "),

//create a "grouper" column
    #"Added Index" = Table.AddIndexColumn(#"Filtered Rows", "Index", 0, 1, Int64.Type),

//check if cell contents are all digits
//  if so then copy over the Index value else write null
//  Then fill down
    #"Added Custom" = Table.AddColumn(#"Added Index", "grouper", each if List.ContainsAll({"0".."9"},Text.ToList([Column1])) then [Index] else null, Int64.Type),
    #"Filled Down" = Table.FillDown(#"Added Custom",{"grouper"}),
    #"Removed Columns" = Table.RemoveColumns(#"Filled Down",{"Index"}),

//Group by the "grouper" column
    #"Grouped Rows" = Table.Group(#"Removed Columns", {"grouper"}, {

    //create a list of the first row in the subtable concatenated to each of the other lines
        {"new csv", (t)=>List.Transform(List.RemoveFirstN(t[Column1],1), each t[Column1]{0} & ", " & _), type list}
        }),

//Remove the "Grouper" column and expand the List column
    #"Removed Columns1" = Table.RemoveColumns(#"Grouped Rows",{"grouper"}),
    #"Expanded new csv" = Table.ExpandListColumn(#"Removed Columns1", "new csv")
in
    #"Expanded new csv"