For devil stones I managed to at least somewhat influence the amount I got. (not editing the amount but changing the xp gained towards recieving new stones). This gave me an easy 4000-6000 stones in a few tries
1. Start a new game with highest xp gain (in my case hard 10)
2.Bevor you enter the first stage search dword - 444442 (value 0)
3. enter a normal fight (not elite!) and collect rewards
4. search for 444432 (value 10) - this is the amount of slain heros
5. change the amount e. g. to 99821850 (value 100,000,000) with freeze normal
6. enter next normal fight
7. collect rewards and close the game like in the gold example
8. restart game and withdraw to end screen
9. you should now get a few thousand stones for rebirth xp
actually i need a few tries but was enough for me to get everything i wanted from packs ?