How can I change the sequence for TAB-ing through fields in a form (in Pan X).
With the form in graphics mode go to the first tab pane of the Properties panel which is the Form Properties. There you will find a popup button for Tab Order which will allow you to set the order to Back to Front (default), Natural or Data Sheet Order.
The default is supposed to be Natural, and I just checked and that is what I am seeing.
There is no documention in the Panorama X help yet for Tab Order, but it works exactly the same as it did in Panorama 6, see the Panorama 6 Handbook from page 670-671.