Hello,
Gantt doesn’t have a built-in feature to make it work that way. You will need to manually implement a custom solution.
For example, you can return HTML elements in the label parameter in the column configuration:
https://docs.dhtmlx.com/gantt/desktop__specifying_columns.html
By applying some styles, you can try to make the elements look like a table.
Here is an example of how it might be implemented:
https://snippet.dhtmlx.com/5/38ec27ab5