If you modify a unit with modding it will only show up on your mod

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I think TERRAINFIGHTER had your answer here. If you want your mod to work in-game, then you need to mod the game when you run it.
Say for example you modded unit 191 to look like your second Lurker. When you mod the editor and place your second Lurker, the only thing it remembers is unit 191 was placed at the position you chose. Then when you open the map in normal StarCraft, it creates a unit 191, but because you haven't modded StarCraft you get whatever unit Blizzard created for unit 191, which would be unused and probably would crash the game.