How do I design a level using random prebuilds walls?

Hello everyone,

I have this question about prebuild objects. I have seen several examples about this like this great tutorial: https://howtoconstructdemos.com/generate-random-levels-from-pre-built-scenes/ but my problem is a bit different.

I want to build a level with just placements sprites that will be replaced by prebuilds walls. My intention is to level design an entire level with a different look each game. To be more clear here is a scheme of my intention:

As you can see, I have 2 sets of different kinds of walls with differents prebuilds. Of course I want them to eventually be duplicated, and that's not a problem.

Seems the solution is to call a function but in all previous examples, it doesn't multiply the presets, so the level is limited by the number of prebuilds available.

Any solution is more than welcome!

edit: in the end, the prebuilds objects are supposed to be 3D objects but I made it simple for now.