Would a written list of session code words add further intention, compared to creating it in the mind only, and perhaps having it fade from memory over time?

If this is a kind of ritual done by the practitioner to honor the process, it would have a benefit in adding further intention. But the primary benefit of carrying out a session and assigning a code word is to create a kind of contract with the divine realm to step in and replay the session that is on record when that originally took place, and was given the code word in the first instance. It is that intention that is repurposed each and every time the code word is mentioned. So there is nothing substandard in simply having a list of code words alone or a master list to which the code word has been added on its creation, and thereafter does not need to be even referenced individually, because the divine will trace the instructions for the master code word and will know to look for every session done along the way as they will all be linked together and corded to the master list and its master code word. So some additional intention can be added by ritualizing the process, and that is an individual preference that is always honored because, like all rituals done for a high purpose, they will add energy that is divine.