How do I get into safe mode with Open core from the opencore bootloader menu?

Does anyone know how to get into safe mode (or insert any other boot args) from the opencore bootloader menu screen?
I know I can add boot args when I have already booted into the desktop (using opencore configurator or propertree etc), but how can I add any boot args at the boot menu?

I tried holding shift when booting but nothing happens.

Fyi I am using OC 0.5.9