how can i add a custom item field to a sales order sublist?

im trying to add an ITEM FIELD to the SALES ORDER item SUBLIST

Patrick already told you, it's a custom column field, is that not what you want?

if I source it from an item field, will it display the right value>

Yup, should do!

Create a custom item field on the item record and then create a custom transaction line field sourced from the custom item field

^^ presuming you're not pulling a standard field value from the item

ok great thanks so much!