Let me share our experience with performance optimisation of our Elm app and looking for bottle necks. Usually is good to use browsers dev tools for performance profiling. At least we did it, but it’s not easier to follow compiled Elm code even if you do not have minified it.
So for our development purposes I made few simple regex which could help us to easier identify which function call is responsive for slowness.
Here you can find all details https://github.com/janjelinek/elm-performance-debugging/blob/master/README.md
Nothing fancy, but maybe it can make someone’s live easier.