How to Devilver with Alpha ? can't see any render with alpha

Hi,
I'm new to Resolve, I placed in a montage some clip who has an alpha channel output.
If I render this I don't see any alpha channel in my renders (qt animation, prores 4444 etc, exr)
The v14 doc says to check the "export alpha" who isn't there

Export Alpha only works in Individual Clips mode, which imposes some other restrictions, though.