[KevinH]

Go to the Sigil MainWindow View menu, then to toolbars, then uncheck whichever toolbar sections you want to hide.

I regularly do this with the Donate button as it is unused.

Some toolbar icons are in their own sections, while others are not. If there is demand, I can change things for a future release to make a specific icon be in its own section to stand alone and be more easily hidden.