New documentation available at https://docs.openkm.com/kcenter/
The documentation at the https://www.openkm.com/wiki is definitivily deprecated.
Consider only use it, if you are user of OpenKM version 6.2 and older.
Click in the banner to close the warning.
Select some filebrowser rows.
Execute the action copy will be shown a destination folder popup.
Click Copy button. All selected rows will be copyed to destination folder.