what are best practices for tracking internal campaigns like cross sell activities? Should it be treated as a marketing channel from the marketing channel reports? Simply add another marketing channels called internal and work with the query string parameters? But this would obfuscate effectiveness of acquisition campaigns which lead to website, because most likely the last touch attribution would then be an internal campaign.
What are other alternatives? Simply put it in an evar?
I would recommend setting up a new evar that is tracking the internal campaign tracking code, as you can control the expiry of that evar as well. Another way of handling this could be to maybe look into product finding method instead or addition to internal campaigns, as this adds more value to your reporting. At the end of the day, you want to see what functionality of your website works best and which internal campaigns it can be be driven by. Have a look at this article that describes product finding method. https://analyticsdemystified.com/adobe-analytics/product-finding-methods/