There are few ways to show multiple projects in same report view.
Either you publish the same report multiple times on the same Jira dashboard and save selections for page filters.
Another option is to create an eazyBI dashboard with common page filters and put separate report for each project.
or you could create one combined report with “All projects” filtered across all imported projects in the eazyBI cube and then publish it either in eazyBI dashboard, Jira dashboard or confluence page
Please find one use-case described here:
Martins / eazyBI