Related to #2805
This is a feature implemented in D8 by https://www.drupal.org/project/coi and https://www.drupal.org/project/config_override_core_fields
Config Override Inspector provides indicators to administrators where form fields represent configuration that is overridden.
This module is especially useful for developers working on sites where there are configuration overrides in place depending on the environment. It prevents confusion that arise when changing a form setting, but appears to not take effect.

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There is a Drupal 7 contrib module that "lets the administrator see all administration pages in her preferred language" and which could be ported to Backdrop: https://www.drupal.org/project/...
Allow admin to select admin language seperate from front end language (multilingual)
@stpaultim – You're right: my approach affects also the main menu. I guess, because menus are also considered as user interface (not as content). @findlabnet – If I didn't miss anything,...
Allow admin to select admin language seperate from front end language (multilingual)
Go to the account edit of the desired user. On the horizontal tab below "Region and Language," select "English" or another language. WFM.
Allow admin to select admin language seperate from front end language (multilingual)