Reference a column from another table in "Add custom column" - PQuery

      Hi,

I would like to perform a List.Positionof, and I need to access a column from another table (the list). When I call for the Table "Combo_lookup" and then try to write the column, I only get the columns from the current table. 

Is there a way to do this? I just saw a video on youtube (although it was PQ for excel), and they perform this without problems.

Thanks