How do I center the submit button?

Go to Forms → Settings → Custom CSS & JS, and at the Custom CSS (All devices) field add the following CSS code.

12
3
45
678
9
10

.quform-element-1_2 {    float: none;
    margin: 10px auto;
    width: 110px;}
@media screen and (max-width: 767px) {    .quform-element-1_2 {        width: 100%;
    }
}

.quform-element-1_2 {
    float: none;
    margin: 10px auto;
    width: 110px;
}
@media screen and (max-width: 767px) {
    .quform-element-1_2 {
        width: 100%;
    }
}

• On lines 1 and 7, replace 1_2 with the Submit element unique ID
• On line 4, adjust the 100px number to the desired button width to perfect the alignment if needed
• On line 6, adjust the 767px number to the desired screen size that the button should become full width for better usability on mobile devices