Last time i checked, you can manually edit the savegames, they are in plain text format.
Only restriction: The game uses some kind of checksum, so the total number of characters in the savefile has to be identical. If this doesn't match the original savefile, it won't load into the game.
So you cannot e.g raise an NPC stat from 1 to 100; you have to increase it from 1 to 9 in the savefile, then load it into the game and do some activity to reach 10+.
Now you can go from 10 to 99, repeat ingame for 99 to 100+.
Also, never skip any obvious breakpoints, like for the skills / stats of the MC. These have to be reached naturally to get the corresponding benefits applied. So if a skill levels up at e.g. 600, you can cheat it to 599 and advance normally ingame.