If user has slow layout, we don't know where the cause exactly is. We have to test each field or groups of fields on layout with 100+fields (trial-and-error procedure). Layout profiler feature would be great! Then we could test each layout and improve its loading time.
The output of layout profiler could look like this:
field 1 - 10 ms
field 2 - 50 ms
portal 1 - 200 ms