Specifically, the multitasking controls button is accessed in the status bar. However once selected, VoiceOver does not indicate that the menu is open, and you cannot simply swipe to enter the open menu. Instead you need to move off the status bar, and return to it to find the controls.
Open an app.
Navigate to the status bar with VoiceOver.
Swipe all the way to the right to find the button to open multitasking controls for the app.
Select the button. VoiceOver focus is now stuck on that button, with no indication that the menu has opened, and no ability to swipe into the menu.
After selecting the button, leave the status bar.
Then come back to the status bar and swipe across again, you should now be able to access the menu.