Thanks for the suggestions!
You can add addresses for the guest already. Open the booking (or quote) and click the Info tab. Click the Change button and add/edit addresses in the place provided.
If the booking and quote are linked (meaning they booking was created from the quote originally), then any guest email/phone/address will update in both places at the same time.
We do show "Repeat Guest" on the booking if the guest has occurred in the past. To see what I mean, create another booking with the same email address and you'll see (on the booking overview page) a little "Repeat Guest" badge with the links to other bookings. The same will show on guests and inquiries if the guest has booked in the past.
If you want to add custom sources (or listing sites) you can do that as well. Open Settings > Listing Sites. On the right side, you can add custom listing sites. This isn't really a "source" exactly, but you could use the field for now to put other pieces of information.
Hope this helps,