Describe your issue or idea
Currently, the default value field when editing a field does not support having more than one default value. It would be nice to have the ability to add more than one default value in some cases.
From my testing, it appears that most of the internal functionality for this is already in Backdrop, and all we need to do is modify the form for editing field settings.
Based on the Drupal core issue here: https://www.drupal.org/project/drupal/issues/1482386.
PR by @hosef: https://github.com/backdrop/backdrop/pull/2349
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