By default, any Button Module will have a fixed height. The fixed height can be changed by setting custom values for the Padding Left and Right. However, sometimes, we need the Button module to be 100% of the width of the available space.
How to set the Button Module to be full-width:
Open the Button module's modal Settings Window
Go to the Advanced Tab
Scroll down and open the Custom CSS Options Group
For the Main element type in
width: 100%;
Bonus Tip: We can set the alignment of the text inside the button using the Button Alignment option in Design Tab > Alignment