Is there any way to make the title (the "May 2021" text) in the echarts tooltips bold / bigger font size?
In the documentation, there's nothing mentioned.
Using the "hacky way" and updating the CSS can be a bit resource-intensive on the client-side as the tooltip is generated on each mouse move. - thus looking for a more clean solution.
Find the chart container, after find the coresponding div element, and from the inline CSS or javascript or Jquery change the font-weigth and font-size, but with text "!important" to override the existing css values.
If you paste the desired code here, I could help exatly with that code!