Allow us to open bookmarked pages on a new tab, clicking from the bookmarks toolbar, without having the menu that is deployed from that toolbar disappear (so that we can keep clicking and opening other bookmarked pages)
Good point, I didn't realize that, but that's a good workaround.
Doing it from the (horizontal) bookmarks-toolbar is something I was used to from chromium browsers. It's a nice to have detail for me, but less of a priority now that I'm trying the same thing with the sidebar.
It is an essential feature. Most of the time I control-click two or more bookmarks to open them in a new tab. I don't want the menu to be closed when I click a bookmark.