SUMMARY Currently, when you press the eraser button of a stylus pen (wacom etc) when in presentation mode, nothing happens. It wouĺd be nice to see the eraser button to erase annotations.
Does it work to assign the Wacom button as a shortcut in Settings -> Configure Shortcuts? If so, it might make sense to set this shortcut by default. Setting shortcuts is a bit glitchy in Okular. The key question is whether pressing the Wacom button changes anything on the „Custom Shortcut“ button.
No, adding the button as a shortcut is not possible.