You could create workflow attach to these 2 lists, and use create a new item to the merging list when new item is created in these 2 lists. And additional
actions to make it better is all depends on these 2 lists’ structures.
And the merging list could be created using 2 lookup columns to get ID columns from those 2 lists. Add when we create lookup fields, you could select
additional fields from those 2 lists, so that you could be able to get all related fields according to the fields you select in lookup fields. And then we don’t need to afraid the changes of those 2 list fields.
Since the merging list could be a custom list, it will allow us to filter columns by select value from column menu and order by and group by operation
also could be set in View settings page.