No, only via Custom CSS and tricks you can do that, sorry.

For example, make preview of CSS used here: https://demo2.joomshaper.com/2026/agentik/

where is the custom CSS?

You have to create it, we don't have it in Helix documenation yet.

I would start with

#sp-header {
  height: 72px;
  width: 100%;
  position: fixed;
  z-index: 99;
  background-color: rgba(0,0,0,0) !important;
  box-shadow: 0 0 0 0 rgba(0,0,0,0);} 

you can set different height