Common guys, these threads asking for this have been in place since 2017…
For marketing emails we need either:
1. Campaign hierarchy
2. Multiselect campaigns for a filtered view and combined stats
3. Give that pointless “Pinning” tool in Analyse the functionality to combine emails stats based on what you click
or someone at HubSpot to add them up for us manually 
For many marketing clients, this is a deal-breaker.
Should be an out of the box functionality at starter level, let alone enteprise.
Cheers