2018 Toyota Tacoma
GDI injectors are marked 1,2,and3. Why? Can you change a 3 with a 1 or 2? Can you use snap on scanner to change the number
The part catalog offers four different injectors (1 in manifold, 3 in cylinder head) with three different prices. So I guess the answer is no they are not interchangeable.
Maybe they have different spray patterns to accommodate different geometries? Maybe each bank is different?

Please post all relevant information when asking questions please, like engine type. I'm guessing that you have the 3.5L V6 (2GR-FKS).
This engine has Toyota's Dynamic Force (D-4S) twin injection system. It has a low pressure injector in the intake, and a high pressure injector inside the combustion chamber. That means that there are at least two types of injector for each cylinder.

GDI injectors are marked 1,2,and3
marked where , or how? On the injectors themselves ...?
Can you use snap on scanner to change the number
no