I have a List A that copies items to list B. When list A item is updated, it create the same item in list B with a different ID.
I need a workflow that can update list B without creating a new ID.
This wont be possible. I would say you should create a "related content ID" custom column and update that when you insert into list B.
Also, if you create a (history record?) item in ListB every time an item in List A is updated, you could end up with multiple items in ListB for some items in ListA. You can't have multiple items in a list with the same ID.
As Cassy says, you need to have a reference column in ListB that points at the "parent" ID in ListA. If you make this a lookup column, Sharepoint gives you a limited set of relational-like capabilities (e.g. cascaded or restricted deletion of child items, and lookup of a limited set of column types from the child back to the parent).
ID is mandatory created in ListB,As far as I understand your problem is "Copy Items" will create multiple items in ListB on each updation and creation which you dont want instead only one item should be there in ListB
Do the following easiest step
Retrieving data ...