Bokeh: Force onclick event to a Legend via JS callback

Question

I'm using Bokeh 2.3.0. I have several items in my Legend that are all muted on load. I provided a button that I want to use for toggling the visibility of all legend items.

Here's what I have now:

Here's my JS callback:

I believe I'm close enough to achieve it but setting the muted property doesn't work and I don't know how to send an onclick event. Hope someone can help or confirm that this is not supported in BokehJS.