The ability to change languages of the software itself.
We work in a bilingual environment, and constantly need to switch between French and English.
Karsten Tinnefeld commented
Apparantly I can now install more than one language (e.g., Adobe InDesign CC 2018\Presets\InDesign Shortcut Sets has several directories after changing language and installing again), but unfortunately there is no option to start it in a specific language.
Tobias Wantzen commented
Besides this it would be extremely helpful, if every localized version of InDesign has the ability to switch easily to InDesign's native language »English«. This would help everyone communicating in the forums with the right terms of UI texts, and it would make scripting easier, because all scripting »commands« are natively in English.