Performance of the DS editor slows down with large projects

If the project has +1000 qml files, there is a delay secs when switching from one file to another. Already at ~500 files the feedback starts to get slower (0,5 sec or so). It would be good to perf test with profiler to see where time is spent. During the pause, the UI is totally unresponsive.

This can be reproduced by creating application that has basic qml file (drawing a rect) and copying it over many times.