Hello,
Gantt doesn’t have a built-in way to do that.
It is possible to display the cells in the timeline if you use the static background and increase its height via CSS: https://snippet.dhtmlx.com/5/02d11aa7a
However, there is no easy way to do that same for the grid. You need to implement a custom solution by using the Gantt API and Javascript.
If you want us to implement it for you, I can contact you with the Sales team.