Grimrock

In Grim2 it is possible to create a new dungeon in the dungeon editor and then in the dungeon editor file created,
change the last line...
dungeonFolder "mod_assets/scripts"
to...
dungeonFolder "assets/dungeons/grimrock2"
and the original Grim2 dungeon will be loaded for modders to check out.

Is something like this possible with Grim1?
If so, what would be placed in the last line?

It's not since the LoG 1 dungeon was created before there even was an editor.

However .. you can check out Komag's outstanding remake of Legend of Grimrock if you want to check out how things work.