From @philsward in https://github.com/backdrop/backdrop-issues/issues/4829#issuecomment-781...
Also, both Themes and Modules need a "remove/delete" option to completely delete them from the file system. Once a theme or module is installed through the GUI, there is no way to get rid of it from the GUI.
GitHub Issue #:
5320
Recent comments
I don't think there is currently a way to set back references in bulk for existing books that already reference an author... I believe you can do this with CER through the UI...
Backlinks for Entity Reference?
If choosing the Views approach you can also use https://backdropcms.org/project/eva which allows you to place the list with more flexibility.
Backlinks for Entity Reference?
Thanks. It still took a lot of trial and error for all the settings within the settings, but I eventually got it to display based on these instructions.
Backlinks for Entity Reference?