Last discussion remotely related seems to be from 2017... And I can't find anything that addresses what I feel should be a configuration option.
I appreciate the ability to turn on/off the elements in the sidebar - but really wish that I had the ability to re-order them similar to the way I'm able to just drag an extension left or right in the toolbar (noting @ant8672 had great points in this post: https://forums.opera.com/post/171456 regarding organization).
I want the Messenger, WhatsApp and other default elements on the sidebar, but I want to move those communication items down, out of view so that I'm less distracted by (but not removing) the notifications on them. Conversely, the note-taking extensions I added to the sidebar I'd like to have at the very top, as I use them ALL the time.
If you're going to allow ordering of extensions, then it just makes sense to allow ordering of these "extensions" as well, albeit vertically on the sidebar instead of horizontally as on the toolbar.