This feature request has been updated to include all plugins in FX Collection 2 which do not have A/B functionality.
Unlike Arturia's compressors which have A/B functionality, I am surprised to see that this feature is missing in other plugins in FX Collection 2.
I think this should be added to an update, as not having A/B will slow down workflow for many producers. Ideally, let's please not stop at A/B, though, because having A/B/C/D would be even more useful. One of Arturia's competitors has A/B/C/D on all their plugins, and I have found that to be incredibly useful.
Sidenote: I've been getting into the pre-amps and Flanger BL-20 over the last two nights, and they are sounding very sweet!