Thank you for your post.
At this time, FileMaker does not have a way to determine which Tab is being used. One way around this is to put separate buttons on each tab. Or, perhaps using a see-through button on top of the tabs to take you to a different layout/tab.
Anybody else out there with a good workaround?
you can give to each portal a name, for example 1 and 2...
Going to object 1 will go to the portal in the first tab, going to object 2 will go to the portal in the second tab...
even if the field you are going into has the same name in both portals.