custom column query editor with if, dates and max statement

How do I add a column in the query editor like I did in the "easy" add column using dax?

Data:

This worked:

maatgevende boekdatum = 

VAR date_1 = 'FM Budget'[Ingevoerd op]
VAR date_boeking = 'FM Budget'[Valutadatum]
VAR year_1 = YEAR(date_1)
VAR year_boeking = year(date_boeking)
VAR maxdatum = max(date_1;date_boeking)
return

IF (year_boeking<year_1;
 DATE(year_boeking;12;31); // for anti-dated addings
 DATE(year(maxdatum);month(maxdatum);day(maxdatum)))

In the query editor I have tried Add custom column using

if Date.Year([Valutadatum])<Date.Year([Ingevoerd op]) 
  then #date(Date.Year([Ingevoerd op],31,12) 
  else List.Max([Ingevoerd op],[Valutadatum], type date)

but that gives an error "token comma expected"