[SalesForce] Global Header Bar on custom visualforce page

The straight answer from a platform feature function perspective is no, there is no way to configure this, i agree its a good request from a UX perspective though! Maybe something to raise on IdeasExchange.

While you might be able to hack this through a side bar component that manipulates the page DOM, this is not safe as it depends on the internal rendering of the page which can change at any time by Salesforce, also the sidebar is not always visible unless configured so by the user.

The other consideration is to build a Visualforce page and within it a scrollable region containing your UI. Your question does not really state if your looking for all of the UI the user uses or maybe just certain aspects. So I thought I would throw this option in, just in case. It obviously requires some development skills and is not a general solution, only for areas you build a UI for, which need not necessarily be from scratch, as their is some great components in Visualforce for reproducing the standard UI, but does requirement development effort.

This basically comes down to creating a custom theme layout with custom styling. You will need to create a lightning component that :

implements="forceCommunity:themeLayout"

as follows:

<aura:component implements="forceCommunity:themeLayout" access="global" description="Sample Custom Theme Layout">
<aura:attribute name="search" type="Aura.Component[]" required="false"/>
<aura:attribute name="profileMenu" type="Aura.Component[]" required="false"/>
<aura:attribute name="navBar" type="Aura.Component[]" required="false"/>
<aura:attribute name="newHeader" type="Aura.Component[]" required="false"/>
<div>
    <div class="searchRegion">
        {!v.search}
    </div>
    <div class="profileMenuRegion">
        {!v.profileMenu}
    </div>
    <div class="navigation">
        {!v.navBar}
    </div>
    <div class="newHeader">
        {!v.newHeader}
    </div>
    <div class="mainContentArea">
        {!v.body}
    </div>
</div>

you will notice that each class represents a section/component of the standard layout, you can then add custom styling (and reorder the components) to fit your needs.

once you have created the above component, you will need to assign it to a layout under community settings:

and finally to the page in question: