Within the Opportunity Editing/Creation screen, you will see that there are references to a Responsible Banker and a Primary Officer. While these can be different, the easiest way to handle this on your end is to always match these two fields together. In almost all situations, you'll want the Primary Officer to take the next step within the Required Actions area. If you go to change the Primary Officer in Core iQ, it will actually provide you with a pop-up saying that it will change the Banker listed for the next Required Action.
However, the place where this comes into play most often is through campaigns and automation. As you know, you can have either of these come from the 'Assigned Banker'. In this case, that Primary Officer is what we use as the 'Assigned Banker' for these communications. So if you ran an Opportunity Listing report and had that campaign come from the 'Assigned Banker', then the item would queue on behalf of the Primary Officer.
Please also note that we have an outstanding item to unify these names to avoid confusion down the road.