That DAW looks beatiful, thank you for the reply!
I didn’t know publishing events from the shell invalidates the layout, that’s exactly what I was missing.
Looking at your examples, your approach for exposing the divider position to the user does make more sense. I am also loving the animation 
Was this widget ever considered being added to the iced::widgets module? Feels like a pretty common thing people could use (I’ve found a use for it twice now in my project).