In this video, you will learn how to quickly replace objects in Twinmotion. This can be done by selecting the objects to replace with Twinmotion objects then right-clicking the object and choosing the Replace Object tool. Then simply dragging which objects you want to use to replace and clicking start is all that is needed. Multiple objects can be used to replace and are randomly distributed across all the selected elements. This can only be done with imported FBX models and not direct linked models. Hopefully, this is updated in the near future for easier replacements.
https://dev.epicgames.com/community/learning/tutorials/mPPL/how-to-replace-objects-twinmotion