Hi Marc,

I am assuming you have added this custom field 'Pick Update' onto the Sales Order Line (sale.order.line model, the product table) and not the Sales Order (sale.order model). 

A) To add it to the existing standard table, you will need to go to 'Edit Sources' and modify the xml code directly on the tag of the report. 

It is advised that you create an inherited view for your studio customizations for ease of maintenance.

B) Alternatively, you can recreate the table on Studio using '/' > use 'Dynamic table' > pick 'Order Lines'.
Once you have the new table, you can use '/' > use 'Field' > and select your new custom field.