My immediate specific need is: Put the "indent" and "outdent" buttons on the toolbar.
The most relevant forum question I could find was here, but it offers no answers.
The more general question is of course, "How can I integrate more toolbar buttons (beyond those which currently show up in the Backdrop UI)? Perhaps there is a documentation page which I just haven't discovered...
BTW: I noticed in the CKEditor documentation (here) that if you leave the toolbar option blank in the config file, then you automatically get the Full Toolbar. I don't know exactly how (or even IF) this might apply to a Backdrop installation.
And then I ran across this really kool thing!
Is there any way to roll this thing into the Backdrop UI? THAT would be really excellent.
Any help is greatly appreciated. —Eric
For your specific need you could try the CKEditor Indent module: https://github.com/backdrop-contrib/ckeditor_indent
Regarding the general question, the author described the module also as "proof of concept for adding plugins" to the editor. See also the whole discussion thread https://github.com/backdrop/backdrop-issues/issues/3875 .