If I wanted to keep using Arc but found this feature critical, I would make a Space with a single pinned folder that I put all the bookmarks under. Not super ergonomic, but just suggesting an idea to a fellow user.
Yeah, that's the option I was recommended when I was trying to use Arc. But to me that kinda feels like getting an Android phone and putting a launcher and skin on it to look like iOS. If I'm gonna switch, I want to switch because it works for me, not because I can coax it into behaving close enough to the way I want, you know? Especially for as radical change as Arc is proposing. So I just decided it wasn't for me, even if I like a lot of their other ideas.