On opening Vegas Pro 11 and 12, I do not see a native Vegas Pro FX called 'Flash". Maybe there was a 3rd party FX called Flash that was installed all those years ago.
Former user
wrote on 7/27/2023, 3:07 PM
Just found something I quite like, Flicker Control has some presets (it doesn't 'flash'), I've used it before to give a sort of strobe effect (S_Flicker is better for strobe effects), but adding Flicker Control to a moving video adds a sort of motion blur, time trail type effect 👍