I don't think it's very common to toggle high/low rates often during flight, but I will take a note of your suggestion and consider it. (In fact, I have been thinking of removing the high/low rates option altogether since it's mostly just remained from the very earliest versions of the simulator).
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No, no, please don't remove this option! It makes the program much easier to use. You can switch between fast and slow with just one click. ;) But if you remove it, you'll have to interrupt your flight, go to the settings, twist and turn and move the sliders. A waste of time, you understand? So please, leave everything as is. :)