Storing the viewport position with shortcuts CTRL + 6-9 should allow you to recall that position with by pressing the corresponding number key.
  1. Move the viewport and press CTRL + 6
  2. You should receive the message 'Assigned current viewport position to key "6"'
  3. Move the viewport and then press key 6 on the keyboard
Expected: Viewport position changed to the saved viewport position
Actual: Message is shown 'No viewport position is assigned to key "6"'
Same result for numbers 7-9