When doing systematic review or meta-analysis research, there is often a need to go through thousands of articles. An exclusion criteria in your protocol may be based on language. It would therefore be useful to be able to filter on specific languages in order to easily exclude all articles in specific languages.
I would also find this feature very helpful. Some of my references have “en” or “English” for their language and others do not, and I need my references to be consistent. I want to clear the language field for all but non-English items but at the moment it looks like I’ll need to do this manually.