In Rive, only one artboard can be active at a time. When an artboard is active, its contents are visible in the Hierarchy, Draw Order, and Animations list next to the timeline (in Animate mode). To switch to another artboard, simply click anywhere on it on the stage.
Use enter and esc to quickly move up and down the Hierarchy. This technique can be particularly useful when navigating a complex file. For example, click on a shape and hit enter to quickly access its path's properties. Hit enter again to edit its vertices. Esc will bring you back up the Hierarchy until you reach the top level, where it will deselect all.
Use the minus (-) and plus (+) keys to zoom out and in. To quickly set the zoom level back to 100%, use Cmd + 0 on Mac or Ctrl + 0 on Windows. Use F to fit the current selection to the max available space. If nothing is selected, this will fit the currently active artboard to the screen.
To quickly pan around the stage, hold right-click on your mouse and drag. You can also hold spacebar and drag the mouse.