Does anyone have this code? I Only found Quick JP Up, at PSX this cheat really helps me a lot.
Here are a couple lists for you.
Note: I did notice a few minor potential issues with some of the codes on the second site while skimming through the list. Also, I have not tested the codes found on the following sites and as such do not claim that they will function as desired and take no responsibility if they have undesired effects if you choose to make use of them.
Link 1 (https://forums.ppsspp.org/showthread.php?tid=9347)
Link 2 (http://gaminglegends.forumotion.net/t18-final-fantasy-tactics-war-of-the-lionscwcheat)
They do not contain any simple "JP never decrease" codes... Although the "Max Job Pts" codes might be suitable for your desires since you stated that you did not have qualms with "Quick JP Up" codes.