By default, the platform does not have this option. You can use the following CSS code.
Please follow the steps below:
1. Go to BuddyBoss > Theme Options
2. Under Custom Codes, enable CSS
3. Append the following:
.bb-template-v2 .primary-menu>li.current-menu-item>a { border-bottom: none; }
4. Save changes.
Screenshots
Without code

With code
