I’ve already tried to set the user attribute on the client. The problem is that it’s session wide not browser tab wide (application wide).
If the same user attribute is set in an additional browser tab, it gets overridden resulting in both browser tabs having the same user attribute’s value.
I wanted to archieve that the same user attribute could have different values in different browser tab.
You can distinguish browser tabs only by the fact that they have different instances of AppMainWindow. It can be obtained everywhere on the web tier using AppUI.getCurrent().getTopLevelWindow(). So you could make a parameter stored in the main window and pass it to middleware services as an additional argument.