Modding noob here and I need help

Ok, so using the Resource Manager for AoE3, I’ve managed to find this among the all the gr2 under Art in AoE3DE folders. As someone who have played both DE and War of Liberty, I have also made some scenarios using scenario editors. However, I do wanna expand my limits and creating my own mods with tons of stuffs added to it…all the plants, animals, new units, new buildings, new props/embellishment, new mineral resources…etc.

Now, with this piece of unfinished tobacco plant, ok so supposedly I can add color to it. And after I do that, how to turn it into something I can add into a map/scenario editor under the “nature” section of scenario editor? And this is just the first step. I also want to add things to the “paint terrain” section such as tilled soil and soil with vegetable to it (like the ones in the mill…just for visual effect of course)…how to do it? How to turn gr2 files into something that can be created in scenario editor?