It is possible today to highlight a folder and select CTRL+I . This will make none of the photos been scanned.
But with several (100-1000+) folders this is alot of work.
My suggestion is its better to disable by all folders (everything) at start and enable folder by folder.
This would also help identify - if a folder is giving problems with lag/hanging or other misbehavior.
And also that the face engine just checks the folders you want it to work on.
