alt Hacker NewsThere is a subtlety here. Having a configurable UI requires that all the buttons and menu entries have a somewhat consistent behavior among themselves. That isn't the case sometimes.
For example, if the GUI can have more than one instance of the same view open, toggle buttons for view modes become specific to individual view instances. Putting those into a global toolbar is wrong.
There can certainly be subtleties. Though in your example, I would argue the mode toggles then belong in a toolbar on each of the instances, which would be a configurable toolbar just like the global one.