AFTER subscribing.

1. right click the game in your library
2. hover over manage and click browse local files.
3. open mods folder
4. find the folder for this mod and open it.
5. open main.lua with notepad
6. find this specific line:

local settings = { key = Keyboard.KEY_G }

7. go to this website to get the keycode of the desired key you want to smelt trinkets with

https://www.toptal.com/developers/keycode

8. enter the number in place of the G in the line showed in step 6

you can change it this way until the mod author integrates this mod with mod menu :)