Hi Capitan Punch, Welcome to the Forums,
I just wanted to confirm that the Foliage tool does look to be missing in UEFN. I’m not sure specifically why. (In my mind, it’s just a tool for placing/managing instanced static meshes)
You’ll see it in that drop-down if/when it gets re-enabled.
Thinking in the long term: I imagine the new ‘Procedural Content Generation’ tool will make it’s way into UEFN before too long. (Different system, but seems like it could be a good alternative to Foliage tool)