How do you connect QuickBooks data into a custom-built dashboard/agent?

The builder stores API credentials/tokens for each customer in an env file - different tokens per client. For a single-customer dashboard, only one set of API credentials is needed. To scale to multiple customers, the plan would be to copy the page structure for each additional customer and add a summary view tying them together (similar to how Keeper aggregates across clients), with each page tied to one QuickBooks entity.