I needed the same thing for web mockups, decided to tackle it for myself. The problem between Affinity Designer vs. those tools is that those allow for multiple shadows to be layered onto each other on a single layer, whereas Designer only allows for one outer shadow on each layer.
I was able to approximate most of the elevation shadows, though a few were too close to others to worry about much (1dp and 2dp for example), seeing as I made this for mock-ups anyway I didn't think that'd be a big problem. They're definitely not the most accurate but can be good for getting a concept out
Material Shadows.afstyles
