You can bring back the Viewport tab by going to Window → Viewport. There will be a checkmark next to the name when its opened. You can re-open the event graph by double clicking the “EventGraph” under the “My Blueprint” Tab. If the My Blueprint tab is closed, you can reopen it the same way you opened the Viewport under the Window option.
I accidentally closed the blueprint tabs (Viewport, Event Viewer, etc), how can I get them back?
I tried Window->Reset Layout, which didn’t work.
What worked for me was opening the Class Defaults and then opening the full blueprint editor
Sorry, I forgot this was different if the blueprint was currently empty! What you want to chose is the “Class Defaults” tab. From there you will be able to open the full blueprint editor.