For the upsell products it might be more robust and user friendly to use collections instead of individual products for the upsells.

When changing anything related to upsells that are used in multiple events you're required to manually change it for every event. This is repetitive and prone to errors where one uses a different order or forgets to add a product. If for each event you can select a collection with upsells for the event then changes only have to be done 1 time and there can be made use of the list and order in shopify instead of creating a separate list.