Thanks for your idea Foffern! We'd love to know more about how you imagine this working. Where would you expect this control to live?
In the meantime, this is a workaround, but if you use an expression to set an absolute value, it will override your keyframes. It's as simple as Opt+Clicking (or Alt+Clicking) on your stopwatch and then typing in the value you want to override with. You can then use the Enable Expression switch (it looks like an = [equals sign]) as a "mute" button.
Hope this help
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