Pamela,
Ahhh, I was in E9 mode, sorry! And for some reason, I thought I'd remembered that we could access the Field Merge Details directly from the Email Template UI in E10. It appears now that I've checked that you can only create a new Field Merge - not, as I thought - edit an existing Field Merge. From a usability perspective, it would be nice to do both.
Best of luck as you dive further into Eloqua and Topliners!
Cheers,
Kristin