Hi Mick,
I'm not sure I'm clear on what your asking -- but I think this is it:
On the Registration Sequence screen, on the far right, you'll see a spot where it can say "Stop", or "Top" or "Next". Set it for "Next" by tapping it.
Now make sure the two registrations are named so that they follow each other. ie: "SongName-1" and "SongName-2"
Once that's done, when you step through the sequence of SongName-1, when it reaches the end, will automatically step to No.1 of SongName-2.
On the other hand, if you are trying to combine them all into one registration, then go to the second registration bank and select the first registration. Then load the first registration bank, and before doing anything else, hit save and '9'. Then re-save the first registration bank. Repeat these steps for the 2nd registration, moving it to 10 and re-saving once again.
Hope one or the other of these helps!
Have a great day!
Adam