Error in PQ - Expression.SyntaxError: Token ')' expected

Table.TransformColumns(#"Grouped Rows",{"First Transaction Month", Date.StartOfMonth,Date.Type})

or 

Table.TransformColumns(#"Grouped Rows",{{"First Transaction Month", Date.StartOfMonth,Date.Type}})

For a single conversion, you can use either {} or {{}}

Hi, it is all about the second argument, you should provide it in a list. IF you are going to transform values on a column, you just need to use one List sign, but to change the values on more than a column, you have to provided a list including one sub list for each column, so revise your formula to=>


Transform a column = Table.TransformColumns(#"Grouped Rows",{"First Transaction Month",Date.StartOfMonth,Date.Type})


Transform two column= Table.TransformColumns(#"Grouped Rows",{{"First Transaction Month",Date.StartOfMonth,Date.Type},{"Name column 2}, each _+1})