I would not recommend doing this because I believe it is what causes you to get banned. Editing your score will show 99,999 on the cup, however your tour score will be much higher, showing 99,999,999. It's probably even higher than that but 8 digits is the max that it shows, so this is easily detectable by Nintendo. If you still want to do this, you will need to search for the action points in XOR encrypted. Your action points are:
Points on the right - base points
If you set GG to pause the game when you have it open you can search and refine pretty quickly. For example you get 38 for a rocket start, you search 38. Then you get 20 from drifting, you search 58. Repeat this until you have 2-10 values left, then you can add to the value. If you know how to carefully edit XOR values it might be possible to set the score you want, but if you add lets say 1000, your score will likely be set to 99,999. On the upside, this will also give you 1M coins at once, but Nintendo is probably basing their bans on both score and coins so its risky business.