I just want to put forward a couple of things that are easy to implement for you and that can save plenty of time to us :)
I went through the settings but I wasn't able to find what I'm looking for. If i might have missed something, well, sorry in advance :p
- add a checkbox to exclude paths that are not in the repository (ie. if you use the composer then you'll have some folders in your project that you don't want to exclude from your project because you're actually using those classes so you need the autocomplete suggestions but still you don't want to search through them because you'll never edit that code). so if I exclude a path from svn through svn:ignore phpstorm highlights those files and folders with a different color but it's not possible to exclude them from a search.
- Folder name filter (just below the "File name filter" would be great to be able to specify a path filter. what if I want to search only in files that are inside a "templates" folder?)