Managing Upsell and Downsell Deals in HubSpot for Revenue Recognition and Compensation Tracking

Hey everyone! For those HS power users, I wanted to ask you how you manage upsell/downsell deals as it relates to revenue recognition and compensation. Specifically: how/where do you capture the delta amount that should be added to your current ARR base. In previous roles I have used a custom object in Salesforce for sub_management but it's a tedious build and clumsy to maintain. Is there a better approach for Hubspot specifically? Or better to buy a point solution?