In the old days, when we wanted a trigger function to "Add X green damage to unit," we would achieve this by creating an array of many Item Attack Damage Bonus abilities that each added a progressive power of 2 of damage. Then, using a change of base for example if you were going to add +100 damage, we would find that this was the binary number
00000000 00000000 00000000 01100100
so then basically just like how we can store any number in a computer with these 32 on/off switches, we would add any green damage bonus using 32 abilities. So in that example above, the 3rd, 6th, and 7th bits are on in the binary number... so we would add those abilities to the unit and remove all the other of the 32 bonus abilities.
Then the unit would see +100 damage, even though he really had a +4 damage, +32 damage and +64 damage skill added to achieve this result. If you do this, you could add any number up to +4294967295 damage by only making 32 abilities in the Ability Editor which is not too bad.
If you google search up the "BonusMod" system for Warcraft 3, somebody probably has all these abilities and the "AddGreenDamage" function already available in some jass library somewhere from 15 years ago.
If you are familiar with
Two's complement - Wikipedia binary representation, you may note that you can also subtract any red damage amount without making more abilities just by using the system above but changing the 32nd of the 32 abilities to subtract instead of adding its damage. Then the other abilities can add back any amount of damage to produce any negative damage bonus, without otherwise changing the system.