Keep historic of visited folders
It's the same with Thunar, so it looks not related to PCManFM, but still it would be great to have this fixed.
Queue file copies
It would help to pick up (for instance) 15 movies from an external disk, one by one...
Queueing files to copy (UltraCopier like features)
Support for HiDPI (for icons in full list view, menus and toolbars)