From the image, I’m assuming you’re trying to use the table structure widget.
To change the width of cells, you can either apply the bootstrap classes “w-25 w-50 w-75 w-100” to the columns or modify the the width in the table properties. I’d advise changing the width in the properties:
As for the height, using the bootstrap classes on the rows don’t work. So instead, I created my own classes to add individual rows:
Hopefully this will help you achieve your goal (: