Bank Statement, Description Across Multiple Rows

Probably most efficient with M-Code.

You can Group by the dates, then concatenate the Description column.

Given your date column, you can use the fourth and fifth arguments of the GroupBy function:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjIwMtE1NNI1MFLSUUpMUorViVbKK83JAfKSU8A8FBWpacgq0jOQeZlZmOqzc5BV5OYh8/ILkHmFRUqxsQA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Date = _t, Description = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Date", type date}, {"Description", type text}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"Date"}, {
        {"Description", each Text.Combine([Description]," "), type text}
        }, GroupKind.Local,(x,y)=>Number.From(x[Date] <> null and y[Date]<>null))
in
    #"Grouped Rows"

Source Data example

Results:

You will need to consider how to treat the other columns, depending on how they are laid out.