Separate workbook to guide dynamic changes

Hi sarah2, check this:

Just make sure the DELETE column name of Edit Table is "Delete"

Output

let
    T1RawData = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjQwVNJRcitKzEtOBTJCUhNzFRyBjEgg9ixJzVUwUorVASkzJk6ZCVHKLCwJKosFAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Session ID" = _t, Business = _t, Staff = _t, #"Question 1 " = _t, #"Question 2" = _t]),
    T2EditTable = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjQwVtJRcnH1cQ1xBTIUUHCsDkiBCZTvWZKYU4kpb2GJJBaSmpir4AzXkJqrYKwUGwsA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Session ID" = _t, Delete = _t, Business = _t, Staff = _t, #"Question 1" = _t, #"Question 2" = _t]),
    // You can probably delete this step when applying on real data.
    T2ReplaceBlankToNull = Table.TransformColumns(T2EditTable, {}, each if Text.Trim(_) = "" then null else _),
    MergedQueries = Table.NestedJoin(T1RawData, {"Session ID"}, T2ReplaceBlankToNull, {"Session ID"}, "T2", JoinKind.LeftOuter),
    Ad_Updated = Table.AddColumn(MergedQueries, "Updated", each 
        [ a = Record.FromTable(Table.SelectRows(Record.ToTable([T2]{0}?), (x)=> x[Value] <> null)),
          b = if Text.Upper([T2]{0}?[Delete]?) = "DELETE" then null else _ & (try a otherwise []),
          c = try Table.RemoveColumns(Table.FromRecords({b}), {"T2"}) otherwise null
        ][c], type table),
    CombinedUpdated = Table.Combine(List.RemoveNulls(Ad_Updated[Updated]), Value.Type(T1RawData))
in
    CombinedUpdated