Here is a list of things Excalibur can't do. I break them in two categories:
API limitation – this means, there is nothing in API that will allow to do this. Though, maybe I will be able to find workaround.
Premiere Pro bug – it's a bug, so hopefully, it will be fixed at some point by Adobe team.
Paste Clip command won't work with clips that were cut (not copied) in Premiere Pro 2019
Masks (e.g. in Opacity effect) are not supported.
When applying video preset with Lumetri Color, color wheels, curves, anything that has some kind of graphic interface, will be set to default
If preset has colour value with keyframes (e.g. Tint), colours at keyframes won't be correct.
Transition presets can't be applied
When applying preset, all non-linear keyframes will be set to linear