It is possible to customise some aspects of the search interface by using Query configuration entry in the Preferences menu.
There are two tabs in the dialog, to modify the appearance of the user interface (result list appearance), or the parameters used for searching (language used for stem expansion).
The stemming language can be chosen among those that were specified in the configuration file, or later added with recollindex -s (See the recollindex manual). Stemming languages which are dynamically added will be deleted at the next indexation pass unless they are also added in the configuration file.