try:
Code:
Result = Table.RemoveColumns(Table.AddColumn(Table.CombineColumnsToRecord(PreviousStep,"merged",{"Hdr1","Hdr2","Hdr3","Hdr4","Hdr5","Hdr6"}), "Custom", each Text.Combine(List.RemoveNulls(Record.ToList([merged])),";")),{"merged"})
where
{"Hdr1","Hdr2","Hdr3","Hdr4","Hdr5","Hdr6"} is the list of column headers you want to merge and
Custom is the name of the resultant column. The header
merged can be anything as long as it is the same throughout; it really doesn't matter what it's called since it's created then deleted in the same line (of course it mustn't be the same as another pre-existing column name).
There are probably better/more elegant ways!