It must be a plugin, Mesh+, Chromodoris …
Here’s a custom mesh loft component that I developed some time ago in Python. I use it quite frequently. It’s only meant to work with polylines though.
Feel free to check it out:
Mesh Loft .ghuser (5.6 KB)
If you put it inside your user objects folder, it will appear in the Grasshopper Mesh menu.
Here’s an example:
mesh_loft_example.gh (19.3 KB)