It's wierd, but it doesn't seem to work.
SU-A - Open ROUTING - Grid name = Routing; File name = Routing; Form name = WBKLOOKUP
Links and Notes Fields: MTRO.CODE, MTRO.OPER and added MTRO.INSTR just in case.
Added a Column header of "Routing"; inserted the Field name of MTRO.INSTR[1]
Went into an item with a single line routing and added notes in lines 1 thru 5.
In IN-A, under the item hit the routings button and the new column doesn't even show up?! No column, ho header, nothing.