Control over biome spawn

[Hrohibil]

Hi

With Gaia 2021 how do I paint or mark the area where I want a specific biome to be spawned at?? 
 

thank you 

[Bryan]

You would need to add masks, something like a distance mask and maybe a height mask to the spawners or biome. 
Then you can turn on the visualization by clicking on the (eye) next to the color. 
This will allow you to see the areas this would be affected in.