Is it possible to replace values to null/empty in a range?

You can address columns with [ ] and rows with { }. Rows start with 0, columns are usually addressed by their name.

So let's say Column 1 is "Column1" then you would address the range as [Column1]{1..5}  etc.

Another (much crazier) alternative is to perform table surgery like this:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlTSUTICYmMgNlGK1YkG81BFjDFETDBETDFEzDBEzFFFYgE=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column1 = _t, Column2 = _t, Column3 = _t, Column4 = _t]),
    Cut = Table.RemoveColumns(Table.FirstN(Table.Skip(Source,1),5),{"Column1","Column2","Column3"}),
    Skip = Table.FirstN(Source,1) & Cut & Table.Skip(Source,6)
in
    Skip

Anonymous , In power Query when right-click on column and use replace option. null should be taken as blank or null.