Here's one approach that might work. Create a new form with no title, containing the Microflow Label widget - this allows you to create a string to display from a microflow, such as 'Welcome '+$Account/FullName where you have first retrieved the Account object for the current user ([id = '[%CurrentUser%]'])
Having created this form, you can then place it in your UI using the Form Loader widget. This allows you to place it in any form, or (what I think you want) in the header area by setting the shared node ID property and adding a corresponding div to your index.html file
Look at this post Using form loader to display name
I know about the formloader option - and i've already implemented it. But i asked for the "widget" like in the home.mendix.com -->
Try clicking on your name... you will see that a smaller popup below the name is shown with some links like "logout".
I could try to rebuild it using the standard feautures of Mendix... but of course if it is possible i want to use existing code if possible.