This is what I mentioned some weeks ago. I still don’t understand why the two buttons for Widgets Sidebar and Vault Sidebar can’t be permanently visible, which would be logical and consistent.
Unfortunately, this was deemed “visually heavy and confusing” and instead, the somewhat strange little clickable handles were introduced, which only appear on mouseover and are probably completely unexpected for most people. To me, this solution feels a bit clumsy.
My two mockups show how all buttons can exist side by side. I don’t actually find this solution heavy and confusing, but rather just as one would expect.