Currently, items in the sidebar are treated a lot like normal tabs. If I have an extension’s control panel open, for example, I can accidentally close it by pressing Ctrl+W.
I’d expect items in the sidebar to be more stable than not, and only go away if really explicitly removed: Ctrl+W I’d expect to act on normal tabs in the center view, not on items in the sidebars.
I think the feature should include how to identify note tabs from other tabs since ctrl + w on notes tab should work even if the note is on the sidebar. You then use pinned tabs to prevent them from disappearing.
I ran into the same issue: accidentally closed several sidepanel tabs via ⌘W, because it was not visually obvious that they have input focus. I could only get them back by quitting and reopening Obsidian.
I can confirm this although your description considers unwanted behaviour of the properties view which should get more visibility than just additional comment to this feature request. In addition of being unwanted behaviour maybe it’s a bug as well?