To change the droprate for R6, R7, R8 and Kjarr weapons, place the em117_ex_grade_lot.em117glt
file in steamapps\common\Monster Hunter World\nativePC\common\equip
If the nativePC folder or any necessary subfolders don't exist, create them.
Only the file named em117_ex_grade_lot.em117glt
will be read by the game, so you can leave the application in nativePC\common\equip
and create and name multiple files for your own presets, switching them as desired.
FYI
em117_grade_lot.em117glt
is for not AT KT droprate
em117_ex_grade_lot.em117glt
is for AT KT droprate
Thanks to @Asterisk for the droprate table before ATKT
https://www.nexusmods.com/monsterhunterworld/mods/1010
Thanks to @MHhexhexhex for the droprate table before ATKT
https://www.nexusmods.com/monsterhunterworld/mods/473
and @IXXur for the editor template, especially for the load and save file code
https://www.nexusmods.com/monsterhunterworld/mods/507