Modulator is an addon to manage and place (modular) assets in the scene. It invites a new workflow to build your scene with linked mesh data. This means that you can edit a mesh that is shared with other objects. If the vertices are sharing the same local location the assets are fuse-able to one object. I know that this description doesn’t say much. Here, watch this video to get an impression of what you can do with the Modulator:
Remember you loaded assets from somewhere and spent a lot of time fixing or adjusting them? Here is what happened: Watertight meshes are very important in Blender and other 3D software. A lot of functions like loop cuts, solidify, subdivision, physics and booleans need a watertight mesh to work properly. Watertight means; all vertices are merged, and there is no open area. It is also free from interior faces and loose geometry. When you work with watertight meshes you create a workable and flexible situation where you can do much more in less time. Start seeing a watertight mesh like a balloon you can put water in it, and won’t leak. Then remove all geo that is inside.
Fuse-able or merge-able assets are assets that share the same location of vertices when you snap them on each other. After a press on the Join-button, the Modulator will join the objects, remove doubles, delete interior faces and recalculate normals. You can now work properly with the fused mesh, like making loop cuts and use modifiers like boolean and subdiv.
The Modulator is so useful because it invites you to use a new workflow in a three-fold way:
Yes, I will show you, it’s here: https://blendermarket.com/products/modulator