Imagine you're building a house and want to make a few pictures to remember the progress.
You can make screenshots.
I think you should also be able to let minetest generate mts schematics which contain only every node you currently are able to see.
I guess that the mts schematic file size would be a lot smaller than the screenshot file size.
And you can "touch" it.
You would need to save the player's position and look dir, too.
If you used a weird texture pack (one which doesn't let you know which node is which one), you know the nodes of your house, not it's look with this texture pack.