While using the Visual Editor, the interlanguage links menu is greyed-out and inaccessible. Exactly when one might need to refer to an other-language article by opening it (e.g., using right-click > Open Link in New Tab, or command-click). This is a feature regression compared to the sidebar language links. Please enable this menu during use of the editor, preferably automatically opening in a new tab, as do wikilinks that appear the editor.
Topic on Talk:Universal Language Selector
Disabled by Visual Editor
Thanks for the report.
I could reproduce this with the new Vector skin in the English Wikipedia.
The issue is probably in the Desktop Improvements code or in VE. I filed a task: https://phabricator.wikimedia.org/T282255