Well Osiris is the scripting engine so for crafting I don't think you will need to deal with that.
The excelfiles are located in "Data\Public\MYMOD\Stats".
The excel files generate the text files via macros the "generated" files in the folder "Data\Public\MYMOD\Stats\Generated" You can edit them directly or use the excel files to generate new ones using the "all.xlsm" file. I find that generating a file individually like "ItemCombos.xlsm" doesn't work. So use all.xlsm after modifying and saving the file you are editing.
The files you probably need to look at are
ItemCombos.xlsm
Modifiers.xlsm and ValueLists.xlsm(to see what you can add to items)
Stats.lsb (you need to unpack MAIN for this using LSTools).
This seems like the most relevant thread on the subject:
http://www.larian.com/forums/ubbthr...ords=crafting&Search=true#Post561521Anytime I try to mess around with these excel files I copy/paste an entry and change it first to get a feel for it.
Qualifier:
I have not tried to modify crafting.