Ok I think I have found a way to hack Diamonds
Lvl 13 reward is 15 diamond
Lvl 15 reward is 7500 gold
So do a group search 15;7500
Region anonymous Dword
Refine to 15
There'll be lot of 15 results you can edit them with incremental to find the main value or just edit them all both work
Change it to 100000000
I haven't made it to lvl 13 yet so I can't check if it will work but I'm pretty confident that it will work