I'm writing the Quest Log just now, but I guess that before creating the real JSON data using the editor, I will need the sprites, and discuss some technical points with the dev team. If any dev/experienced questmaker can PM me, I'll give details.
- - - - -
Well, my favorite hobby after having asked a question online is : look for the answer myself

So today, I did a few little things :
- Read the wiki
- Installed Tiled
- Downloaded AT's source code snapshot
- Inspected the existing quests/dialogues/maps
- Read portions of the code to understand how everything is linked togheter
- Used Tiled and created 3 of the 4/5 maps needed.
It wasn't exactly a cakewalk, but it was way easier than I imagined. The tools are excellent, and the documentation, while lacking a full tiled<->JSON interface reference, is crystal clear and helpful.
I'm still a bit confused about the content editor, especially on the "conditional expressions" in the dialogues, but it looks like a powerful yet not-that-complicated tool. Many Kudos to those who developped it.
I guess all I need now is some artist to draw the sprites I miss (I'd really like to avoid inflicting my version of "art" to AT players), one or two more days of work (last one or two maps, include all I've written in the correct form in the content editor), and I'll be ready to advance to the review/beg-for-features/debug/test phase !
Edit : Allright, I got it. No one draws these sprites especially for AT. Have to pick from the used tilesets. Luckily, I found almost all I needed
