Part of #378; copied from https://github.com/backdrop/backdrop-issues/issues/2887#issuecomment-405...
I was playing around with D8 core and contrib media-related modules, and this specific feature drew my attention:

...so, media types have this "Field mapping" feature (the screenshot above is for the "Image" media type), which allows you to store metadata information to entity fields. I know we are a long way from anything like that (or are we?), and I don't wanna derail this issue here, but I thought that we could perhaps be using this to be automatically storing EXIF data to such a field (that we could be hiding by default). This could help us retain the EXIF data across any edit operations I believe.
Just a thought.
Recent comments
The specific tags I need are "<ruby>" and "<rt>" Wow, yeah, that's a pain with CKEditor5. A custom plugin, for sure, but no clue, what the code has to look like...
Specific tags to work in CKEditor 5
I think maybe the problem is with CKEditor stripping the tags - it can be more aggressive than what you would expect from the text format settings. I copied your examples into an example page...
Specific tags to work in CKEditor 5
This saved my day, exactly what I had cooked up but I could not find the necessary settings. Thanks a bundle :)
How to relate one view to different nodes?