Custom buttons in Fiori Launchpad Shell Header - only one button possible since Fiori 3.0?

Hello experts,

I am currently struggling with adding more than one custom button to the Fiori Launchpad Shell Header.

It should be possible with the method addHeaderEndItem of the sap.ushell.renderers.fiori2.Renderer and it worked fine with Fiori 2.0 (tested with UI5 version 1.60), but it does not seem to work with Fiori 3.0 (tested with UI5 version 1.71).

To reproduce the issue you can open a FLP Demo App, e.g. the Worklist App, open the browser console and execute following code:

var oRenderer = sap.ushell.Container.getRenderer("fiori2"); 

// First button (displayed)
oRenderer.addHeaderEndItem("sap.ushell.ui.shell.ShellHeadItem", {
    id: "myTestButton",
    icon: "sap-icon://action-settings",
    visible: true
}, true, true);

// Second button (not displayed)
oRenderer.addHeaderEndItem("sap.ushell.ui.shell.ShellHeadItem", {
    id: "myTestButton2",
    icon: "sap-icon://world",
    visible: true
}, true, true);

Only the first button will appear. Am I doing something wrong or is this a bug?

Since the code example of the method addHeaderEndItem also adds two buttons I assume that it should generally be possible to do so.

Thanks in advance,

Julia