Here is what works for me in Wix Studio:

1. Select the menu object. In the Margins section of the Inspector sidebar, dock the menu to the right side of its container.

2. In your main editor window, the menu object should be shown with a dashed line showing the dock connection. Adjust the pixels to get it the right distance away.

3. Set the width of the login bar to be wide enough to fit the longest names.

4. In the login bar settings, ensure the login bar alignment is right aligned. (I right aligned the menu items as well.)