Not possible to use -HeaderContent after v4?

Product: PowerShell Universal
Version: 4.2.10

In the Admin portal, there is no way to set HeaderContent on a page, when using the GUI to edit pages, as far as I can see.
I can add it on the specific pages .ps1 file just fine, but it is removed if any changes is made to the page content in GUI.

Am I missing an option somewhere?