While making characters, I Know that I will only work with symmetrical Morphs. But I noticed that while using sliders, I have to constantly taking care about what the name of the slider is because I Have to Avoid Unsymmetrical modifiers, So with time I'm checking sliders 1 by 1 if they are For Left or Right side, and Locking Them to avoid manipulation errors.
So finally, it's time-consuming and boring.
So my suggestion would be to have a button as a general modifier who would set all Left and right modifiers On or off in 1clic.