Whops, I think I didn't put it in the help section!
The format to write in the item note box is the following:
<Multicraft:Blacksmithing>
<Column:A>
Multicraft needs to be followed by the craft name (Blacksmith, Alchemy, any name you gave to the Craft)
Column accepts A for the left column, B for the right column or All for any column
Hope it helps!