Here are the steps you can follow:
1, Navigate to Online Store > Themes > Edit Code.
2, Locate and open the base.css (or theme.css, custom.css) file.
3, Paste the code snippet provided below at the bottom of the file, then save your changes.
button {
box-shadow: 0 0 10px rgba(255, 255, 255, 0.75);
}
Here is the result on a button
We hope this assists in resolving the issue.
If you find our solution helpful, kindly consider Liking and Marking it as Accepted. Thank you!