Thanks for your suggestion.
Will see if more people ask for this.
Steps to reproduce:
1. Start WinSCP
2. Click Tools > Import Sites...
3. Import any Site
4. Move Site imported on step 3 into any Site Folder
5. Click Tools > Import Sites...
6. Site that was moved into Site Folder would be auto-checked for import.
6. Site that was moved into folder would not be auto-checked for import.
Version: 5.13 (same behavior on older versions) with “Commander” interface on Windows 10 FCE.