Is it possible to hide the floating toolbar?

Which feature are you referring to? The Plotly.setPlotConfig function or the dash dcc.Figure(config=...) attribute?

It sounds like you are referring to the plotly.js issue with Plotly.setPlotConfig? If so, could you open an issue in the GitHub - plotly/plotly.js: Open-source JavaScript charting library behind Plotly and Dash repo and discuss it with those maintainers?

Of course, the workaround right now is to apply your desired modebar on every graph that you use. You can always create your own component classes that provide the defaults that you want, like:

def GraphWithModeBar(**kwargs):
    return dcc.Graph(config={'modeBarButtonsToRemove': ['sendDataToCloud']}, **kwargs)