need multiple group by in power query

Ah, now I understand.

First group by at the lowest level, next group by the higher level, adding aggregation "all rows":

This is the generated code, in which Value.Type(#"Grouped Rows") in step #"Grouped Rows1" is a manual replacement of the generated type table. I consider it a bug (or a mistake by Microsoft) that the nested tables with "All Rows" get type table instead of the type of the original table. As explained in this video (it's a longer video, the link jumps to the relevant fragment).

let
    Source = Table1,
    #"Grouped Rows" = Table.Group(Source, {"account", "date"}, {{"sum of amount", each List.Sum([amount]), type number}}),
    #"Grouped Rows1" = Table.Group(#"Grouped Rows", {"date"}, {{"total amount", each List.Sum([sum of amount]), type number}, {"AllRows", each _, Value.Type(#"Grouped Rows")}}),
    #"Expanded AllRows" = Table.ExpandTableColumn(#"Grouped Rows1", "AllRows", {"account", "sum of amount"}, {"account", "sum of amount"}),
    #"Sorted Rows" = Table.Sort(#"Expanded AllRows",{{"account", Order.Ascending}, {"date", Order.Ascending}}),
    #"Reordered Columns" = Table.ReorderColumns(#"Sorted Rows",{"account", "date", "sum of amount", "total amount"})
in
    #"Reordered Columns"