This is a follow-up of !99 (merged), sorry for taking me so long to get to this.
As Alexander argued in #559 (closed), making this button front and center is not a clear win, the hotkeys (control+r and f5) should suffice, if the user prefers clicking, that action is just an extra click away in the View menu. There is also the gesture "middle click down" in Icon and Compact views that reloads the folder.
Other than that, I don't believe this action is so important to be in the toolbar, users may find other actions such as Split View and Zoom Level as important as it, we would have to add more and more widgets ending up with a bloated toolbar.