This is part of #779 and the same as https://www.drupal.org/node/1513054
Contrary to #933, which is about making title a proper Field API field (which is what the Title module does) and which we determined that can only happen in Backdrop 2.x, this issue here is to simply move things around, and sorta "fake" the title being a Field API field (what the Title field UI and Title Display modules seem to be doing).
After implementing this, we could loose the whole "submission settings" tab by moving the "Explanation or submission guidelines" text field out of the tab set and under the content type "Description" text field.
GitHub Issue #:
1441
Recent comments
For such cases I like EVA https://backdropcms.org/project/eva
Display field using content of another field
If you don't want/need a View, I think Computed Field would be an excellent option for this. BTW, you can use token replacement (by using the function token_replace()) in the computation of the field...
Display field using content of another field
Views would be my first port of call, but I guess you've already thought of that. I haven't used it but you could also look at Views Field Formatter
Display field using content of another field