Stick header in proper scroll position when having a custom fixed topbar on top of it

[vinothkannans (Vinoth Kannan)]

Is it possible to change HTML of header and footer and message details on the forum?

I added custom header in ember plugin outlet above-site-header. Then using below simple css I am hiding it when scrolling

.d-header {
    top: auto;
}

.docked .d-header {
    top: 0;
}

Try this CSS. I hope it will work for any custom header.