How to change the health and shield of all players without changing their teams

So I’ve tested other maps and I believe they are using the class selector and class designer to change players max health and shield. I could be wrong but I think thats how they are doing it. I wanted to give that a go but there is no option to apply class to all players. Only the instigating player can be assigned the class. I’m not sure if I’m missing a setting or if it’s just not possible with the device.