After some playing around I figured how to do regenerative/degenerative skills for HP or MP.
Basically go and make a state for each that you wish to have (e.g. Regenerate HP) then in the first part of the script go to line
1274 where you should see something like
when 2 # 毒
return ["スリップDAMAGE"]
This is stating which states are defined as slip damage either with + or - numbers, in this case 2 so for instance if you want state 18 to be your regenerate HP state then add the number 18 after the 2 so it looks like
when 2,18 # 毒
return ["スリップDAMAGE"]
Now you'll still have to do more so scroll down to line 1302 where it should show
when 2 # 毒
return [["hp", 0, 10, true, true]]
This is basically saying when state 2 is inflicted (poison by default) it affects HP the 0 after HP is base damage the state does per round, the 10 after that represents the % hp damage is done per round. The first true represents if you want the numbers to pop up affecting profit or loss of hp, the 2nd true represents whether the state can cause death. So you can configure those to how you like you can replace HP with MP if you like and the 2nd number in brackets to - to show how much is healed per round. So if you make this regenerate HP you should do this below the poison state.
when 18 # 毒
return [["hp", 0, -10, true, false]]
Almost done now go down to line 1400-1424 and make sure that none of the when statements below that match the skill ID's of your new regenerative/degenerative skills.
That's it, hope someone finds that useful.