thank you for your support.
Unfortunately, the compiler says "ID is not a member of spr". I tryed to write it in lowercase, too.
Anyway, I attempted a workaround.
I loaded AGS 2.62 in a separate directory, and created the Save/Load GUI according to the tutorial.
Everything works fine
So, I saved everything, then I loaded AGS 2.7, and loaded my game with the new GUI.
The room conversion has been applied, as usual, and when I look into the Global Script to see if something has changed, I surprisingly notice that everything was untouched! :o
There are "LoadSaveSlotScreenshot" function calls, and... they works! The compiler compiles the game, and when I test it, it works. The screenshots appear.
I can't figure out why, yesterday, the compiler told me "undefined symbol LoadSaveSlotScreenshot'"...
Well, to be honest, there is a little thing that doesn't work: the very first time I save a game, it crashes indicating that I attempted to delete a sprite that was not allocated.
But the game saves correctly in its slot.
Then, every time I run the game, and save, everything is right.
Maybe it could be useful to change all obsolete functions into the new logic; if I succeed in, I'll post the changes.