Assuming that you have 2 or more browser windows open, if you were to add/delete/edit a bookmark from one of those windows, this operation will not be reflected across other browser windows.
Though BookmarksBarWidget is a singleton, such an object will be created once per process where none share any relationship between the others. Here is a better view of the problem:
It may me due to the fact that their exists no means for browser windows to poll or just make sure that changes made to the JSON file that holds all the bookmarks (file path here) are reflected in their singleton object.
Messing around with Browser Settings, there appears to be no issue applying changes as all my opened browser windows honored any change. Not sure yet how the API works exactly (i.e. the GUI::JsonArrayModel and the functions within the Config namespace), so I can't speak on why using Config's functions seem to work fine given multiple open windows.
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