Evidemment, il ne suffit pas d'appliquer le système de gestion des layers à mon programme de chargement. Maintenant que c'est au point, il faut que je convertisse l'éditeur de niveaux, puis ce sera au tour de l'éditeur de sprites et l'éditeur d'animations. N'ayant pas réussi à faire la conversion "d'instinct", je prends le temps de regarder quels sont les éléments présents sur quel layer dans l'ancienne branche de développement.

Introducing a new layers management system isn't useful before tools are converted to that system, of course. I tried the Level Editor first, but it didn't worked as expected -- i.e. the spriteset on the top screen doesn't show up. The best I could get was a weird layer that mimmic the structure of the tileset, but using plain ASCII characters.
Being for a week-end on my former laptop, I tried showing selectively the layers of an older build, and I could have the "ghost" layer appearing when showing BG1_SUB too. Curiously, it also shows when no layer at all is enabled. Let's just work on the hypothesys that the "Emulation > Layers" checkboxes in desume UI invert what is programmed in the picture engine registers, not hiding the layers. As a result, if defaults (or previous) contents of this layer is "use the same map slot as the BG3 (tileset), use the same colors and characters as BG1 (because the ghost layer is obviously *not* BG1, which is the widgets' text). then you get the ghost out of uninitia...