Ctrl + R
In the files pane, all files (depending on Explorer++ setup) are displayed and sorted. Using Refresh updates the display; the files are re-sorted and re-displayed, subject to current settings (ie. Sort By, Group By, Show Hidden Files, etc.).
Refresh also restores the address of the currently active tab in the Address bar.
The folders pane is not refreshed (ie. rebuilt) by Refresh. Collapsing (clicking the minus, eg. ), then expanding (clicking the plus, eg. ) for a node in the Folders pane will refresh that node.