Description of the need
The "Date format for log messages" field at /admin/config/development/logging requires entry of PHP codes, but we already have existing date/time formats at /admin/config/regional/date-time that people might prefer to use instead.

Proposed solution
Allow people to select from either an existing date format, or a custom format that is entered on the dblog settings page. A custom format entered here would be used for nothing else.
Alternatives that have been considered
- Creating an additional date format presented lots of issues, see https://github.com/backdrop/backdrop-issues/issues/4614 for the full story.
- Original issue: Allow selecting an existing date format for log messages
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)