Changing multimesh /applying it in different ways

Godot Version

4.2.2

Question

So i have made a plot of grass with a mesh that i have made in blender and imported in to godot.

The mesh i used on a multimesh plane. But when i create lets say a world, i dont want me mesh too always be square and i need it to follow the ground if its going up and down. (Dont know how explain it in a simple way more than i want it to be applied as a skin or so) And i want to be able to like “paint” it but its a scene is it possible or would i have to find a different approach. If you know any videos or guides on it, i will gladly accept those aswell.

This is how it looks and the scene tree.

There are a bunch of foliage painting/scattering plugins.