Ok, some small other problem:
I've set the alwaysCreate property on the tab itself, in this tab I've a <Disabled>
After opening the tab-pane everything works fine and the specific tab is not visible.
No I made a test if a specific user may see this tab and if so I made a flow to it. But now the strange thing appears, it doesn't matter if this is No or Yes if there is a flow it's visible. Is this a bug or a "great new" feature. See picture, how I did this:
For best results, use the Firefox browser..