How to active "FXP it 50 times" option

Starts FTP client and from the main menu, click Tools > Script Designer, the FTPRush.pac script file should be loaded in the Script IDE, you may find the "\\" in the line 44, try to remove it first, on the Script IDE main menu click on File then select "Reload FTPRush.pac", close the Script IDE now and connect to any site, right click on the site window, you will see this "FXP it 50 times" menu appears.

How to assign hotkey to FTP script function

Please open the Script Designer window first and load FTPRush.pac file, Add RushApp.UI.Menu.Remote/Local.Add('menu_folder','item_name',position,'hotkey'):=YourScriptFunction in the OnSwitchlayout procedure body.
For example to assign "CTRL + F12" to "FXP it 50 times":
RushApp.UI.Menu.Remote.Add('', 'FXP it 50 times',2,'Ctrl+F12').OnClick :='RefreshAndFXPManyTimes';

What is the CompleteFlag in RushApp.FTP.Transfer

The CompleteFlag param is a perl regular expression. It associates to the RepeatCount param in RushApp.FTP.Transfer, it is used to stop transfers if the folder or file name matching Completeflag in target server.

For example when you FXP directory from source server to another one with a big repeat count in the FTP.Transfer function, the transfers stopped automatically if there is a folder called "completed" matching ([^\w]*100%[^\w]*)|([^\w]*-\sCOMPLETE\s\)[^\w]*)|([^\w]*-\sCOMPLETE\s-[^\w]*)