I would refer to this account aggregation. It’s an idea that fits Monzo‘s vision of being the central hub for your finances and they’ve already started providing aggregation of credit card accounts (albeit in a very basic way compared to other aggregators). I’m not sure whether they have seriously started looking at aggregation of other account types yet.
In the meantime you could look at other dedicated account aggregation apps.
Unfortunately, open banking regulations only apply to payment accounts (essentially just current and credit accounts). They don’t require providers of typical savings accounts or investment accounts to make the accounts easily readable by 3rd parties using APIs.