How to create a fixed header (that doesn't move on page transition) that is present on some but not all pages.

How to create a fixed header (that doesn't move on page transition) that is present on some but not all pages.

Hello! I have a simple application with around 5 views that all share the same header/nav, however it also has a login page that has no such nav.

I am looking for a way to configure the document so that the login has the nav invisible/not present, then once it logs in, it transitions into a view with the nav (I'm using slide transition, but I guess the effects don't matter), and then any further navigations between these 5 views transition all but the header/nav, keeping it fixed. Finally, if the user logs out coming back to the login page, this fixed header should fade out/disappear/slide out.

What would be a way to do this?