Teo Lachev shows us how to build a Power BI report book:
Scenario: Management has requested an easy way to view a subset of strategic reports located in different Power BI workspaces. You can ask the users to mark reports and dashboards as favorites so they can access pertinent content in the Favorites menu, but you’re looking for an easier configuration, such as to create a book of reports with a built-in navigation that organizes reports in groups (like a table of contents), such as the screenshot below demonstrates.
Click through for the instructions as well as a discussion on why you wouldn’t necessarily want to build a Power BI app for this.