how to keep navbar fixed at the top of the site

Could you make the notifications? Could you share the solution if I do it? Thanks!

You may select layout-navbar-fixed from Tools → Advanced Settings → AdminLTE layout class, after that re-generate ALL the script files again.

I was able to get this working in version 2022, without having content covered by the menu, with the following CSS added to the User Stylesheet:

.main-header {
    position: fixed;
    top: 0;
    right: 0;
    left: 0;
    z-index: 1030;
}

.content-header {
    margin-top: 50px;
}