Anima Tree, Void Monolith and Ancient Exostrider Midsection not spawning

[iuriguilherme]

In a custom scenario to start in an abandoned city, the exostrider, the monolith and the anima tree are not spawning.

The monolith can be added in the custom scenario list and even if it's not present, the strange signal quest will spawn it elsewhere, so it's not much of an issue.

The Anima tree will spawn in a second settlement if multiple colonies are allowed, or through the random event in 30 days.

But AFAIK the exostrider will not spawn if it's not present at map generation, and the only way to get it is through dev mode.