Loading resources added after compilation?

I'm making a highly modifiable game, where characters can be created and added in by the user after downloading. The idea is to make the user not need Unity at all to create characters. Right now, images and text files can be read, allowing for 2D, sprite-based characters are working fine. However, I would like to allow 3D Models to be loaded as well, which would mean anim files too. Previously, I was using Resources.Load(), but that seems to only work with files placed into the resources folder at build time, and cannot be added to after the game is compiled.

Is there a general way to do something like Resources.Load(), except for files placed into a folder after the game is compiled and built?

 

I've never done it, but there are some assets on the asset store that claim to do something like what you're looking for.

This one for example:
https://assetstore.unity.com/packages/tools/modeling/runtime-obj-importer-49547