How do i add new field in Update Items from Sales Order

What field are you trying to add? Is it available in the drop down when you press the pencil icon?

Yes i want to add field which is Bom in every line item

I tried to change the Dialog in erpnext.public.js.utils.js but its not working

That would be difficult I would imagine, tbh I don’t know what ERPNext does when you submit an order item with BOM.

Might be easier to submit, cancel and amed?