Objects Replacer is a Blender add-on from Georeality Design built to speed up placing objects or lights on terrain while creating scenery, though it can also be used for various other 3D design tasks. It swaps plain-dummy objects for the final, detailed objects drawn from a self-created source collection or a single selected active object.
By altering its parameters, you can control the variation and mix across a set. Choose whether to create instances, keep the scale of the targets or the collection objects, or randomly apply scales from a given range. The same choices apply to rotation and to the name attributes. You can set the selected objects as targets or use every object in a target collection, and move the final objects into a new or existing collection.
The add-on also allows fine-tuning of how placed objects are randomized. Documentation and demo videos are available for further detail. It supports Blender 2.93 through 3.4 and is released under the GPL license.