Using Language mapping feature you can manage languages (enable or disable) through the plugin directly without going into the admin part. It could be especially useful in case you do not have rights to change channel configuration.
To make language mapping through the plugin you should select on projects' page More Actions button and press Languages
In opened page you can Enable or Disable languages and change mapping between System language (language name which is used in CMS) and Memsource language (language name which is used in Memsource). For saving click Update button.
If during the export you select Configuration which can limit the language list, in opened language mapping page limited list will be displayed too