Want to have a switch to enable/disable auto expand the folder-tree

Comparing between large folders is very slow. I would like to have a switch to control whether or not the folder tree is automatically expanded. I implemented this on my own. But I found that it's actually the recursive scanning comparisons that are the slowest.

The features I want:

1. a switch to control whether or not to auto-expand and auto-recursively scan.
2. this switch is on by default. When it is on, the auto-expand and auto-recursive scan remain unchanged.
3. with the switch off
   1. Only the first level of the current directory is scanned.
   2. Double-clicking on the sub directory triggers a scan of that directory, which also scans only the first level of elements in that directory.