All the helpcenters has special DIVs with the ids as faqprime_desktop_custom_header and faqprime_desktop_custom_footer (on mobile device the corresponding IDs are faqprime_mobile_custom_header and faqprime_mobile_custom_footer) which can be modified using the GTM to add a custom header or footer on the helpcenter.
Note: These IDs are present only in the logout state of the helpcenter.
Sample GTM Code
<script>
var headerhtml = '<My Custom Header>'
var footerhtml = '<My Custom Footer>';
if (document.getElementById("faqprime_desktop_custom_header"))
{
var c_header = document.getElementById("faqprime_desktop_custom_header");
c_header.innerHTML = headerhtml;
}
if (document.getElementById("faqprime_mobile_custom_header"))
{
var c_header = document.getElementById("faqprime_mobile_custom_header");
c_header.innerHTML = headerhtml;
}
if (document.getElementById("faqprime_desktop_custom_footer"))
{
var c_footer = document.getElementById("faqprime_desktop_custom_footer");
c_footer.innerHTML = footerhtml;
}
if (document.getElementById("faqprime_mobile_custom_footer"))
{
var c_footer = document.getElementById("faqprime_mobile_custom_footer");
c_footer.innerHTML = footerhtml;
}
</script>
<style>
Your CSS
</style>