I then added it to the duplicate engineering bay's abilities, and made a command-card button for it. When I use it, it takes the minerals, researches for 1 second, and then has no effect. None on the tooltip, and none on the actual unit stats. I checked by having it add 300 dmg but there was no difference in damage. As is probably pretty clear, I'm rather new to the data editor, so I'm probably just missing something really obvious. Any help would be much appreciated.
it should work i literally just made a custom ability and it seems to fit the way u did it but mine works.. Just check if in your upgrades Effect you have the Units actuall Weapon Effect Damage selected and that Add is selected and change the amount to the number u want and it should work.. and for the button u need to make your own custom button in the button tab in the Data Editor which is self explanatory