What problem does this feature solve?

I want to use only one dataZoom(back or zoom).

how to use that?

When operated with show's boolean, both icons appear or both disappear.

I want to use only one of dataZoom's zoom and back.

What does the proposed API look like?

`toolbox:{

feature: {
    dataZoom: {
          title: {
          zoom: "" //i don't wanna use that(zoom) 
          back: "Zoom Out" //i wanna use back.
          },
  },
}

}`