Description of the need I was looking at styling the tabs slightly differently and realized they don't have any identifying classes (e.g. the "Edit" tab does not have an "edit" class) so are hard to pinpoint precisely with CSS.

Recommended solution
Add a view class to the View tab and an edit class to the Edit tab.
GitHub Issue #:
4207
Recent comments
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)