CrushFTP has lots of plugins that extend the functionality of CrushFTP. Most, if not all of these are provided for free, by myself. However, you are free to develop your own plugins that do other things. The plugins I have are just examples of the sort of thing that can be done through the use of a plugin.
Most plugins can have multiple instances of that plugin. So if you wanted to authenticate against 3 different LDAP servers looking for a valid login, you would click the add button to add additional plugin instances. Some plugins require CrushFTP to be restarted after adding a new instance before the new instance will take effect.
Plugins all have an enabled flag that determines if CrushFTP attempts to use the plugin or not. Technically its still up to the plugin to decide if it should still do anything as CrushFTP still calls. it.
There is sample code and additional documentation available on the plugins. Third Party