Improve profvis performance for profiling shiny app

Question

I have a very large and complex R Shiny app and I am trying to find bottlenecks or parts of the code to improve via the profvis package. The problem is that profvis itself is performing very slowly (because of the processes and functions in my shiny app) so that it's lagging and almost not possible to properly view & navigate through the profile or the flame graph.
Starting the profvis profile via R or via browser (firefox & chrome tested) doesn't really make a big difference here.
I am only testing one (the main) feature/calculation in my shiny app which is initiated by one action button, thus I can't really test less features or make the profile "shorter".

Any help or tips are appreciated. Especially ways to run profvis faster. Another option I tried was to only wrap parts of my code inside the shiny app with profvis, but I didn't find a way to get this work.

Thank you!