Sage released 5.0 SP1 for Mobility not too long ago. One of my beef’s was that to reorder tabs on the BlackBerry form designer you had to basically hack into the database to alter the form XML directly. I am glad to say that in the SP this problem was addressed although in a not too discoverable way.
To move the tab select it and while still holding down the mouse button move it to the desired location. Adding a tab and removing a tab is handled through the context menu as well.
Save your changes and away you go.
It would be nice in the future to see some form of tab designer that allows the movement of many tabs or ones that are not so visible to the developer.