nextcloud-server/apps/theming/css/settings-admin.css

#theming input {
    width: 17em;
}

#theming .upload-logo-field {
    display: none;
}

#theming .theme-undo {
    cursor: pointer;
    opacity: .5;
    padding: 9px;
    vertical-align: bottom;
}

#theming .icon {
    display: inline-block;
}

#theming label span {
    display: inline-block;
    min-width: 90px;
    padding: 8px 0px;
}

#theming .icon-upload {
    display: inline-flex;
    padding: 8px;
    margin: 0;
}

div#theming_settings_msg {
    margin-left: 10px;
}