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
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