The below suggestions are for Design reviewing/evaluation; they are not actual bugs.
(1) If a language that is not presented on the dashboard is entered, the message may be more informative. And the message at the bottom "You can search by language name..." should not be centered.
(2) There is an interesting case - when entering 'tag' - the auto-fill will suggest: 'taglizit' as a valid suggestion.
Also present in production enwiki 1.31.0-wmf.1:
"Selecting" 'taglizit' will display English as the suggested language.
(3) The option 'All languages' should be present all the time.
The initial load without any selection done (the selection refers to the last selection made by a user).
After some selections, 'All languages' option appears.