Background tracks: one muted bar behind every bar slot (grouped) or category stack (stacked / percent), spanning the whole value axis with the bar's width and corner radius (2D).
Optional
Track color (default: theme baseline at 20% alpha, the alpha of ECharts' default track)
baseline
Alpha multiplier of the color, 0-1 (default 1)
Background tracks: one muted bar behind every bar slot (grouped) or category stack (stacked / percent), spanning the whole value axis with the bar's width and corner radius (2D).