How to put faces flat

I’m looking for the name of an extension that I’ve come across which allows one to splay a 3D surface much like one can unfold a box.

This one (Flattery) might do what you want, from its description:
https://sketchucation.com/pluginstore?pln=Flattery

Thanks for that.
Also, is there a way to reverse the “Make Planar” option in QuadFace tools, once you’ve worked on the resulting geometry?

Sorry, I’ve no idea about that.

OK, no biggie… Thanks.