GXT offers TabIndex on most form fields which can be used to set the tabbing order.
Some widgets, however, do not have TabIndex property. To change the tabbing order for such widgets it is necessary to manually change the insertion point into the parent container.
I tried to drag and drop widgets on the explorer pane but it didn't work.
It would be nice to be able right click on a container and select Tab Order... or Widget Creation Order... which would bring up a dialog box with the list of container's children. We could then simply use drag and drop on the list to change the order of adding them into the parent container.