1 structure per world

He explained it kinda weird in the last topic you posted on. Basically just go to the variables section and make a new variable called FirstTimeJoining, and make it initially false. Make a procedure and go to the Triggers and do, "When Minecraft Loads a World" like he said, and then do an "If - Do" Procedure block. 

Go to logic, get the light blue equals block, put that in the If, then go to custom procedures or whatever and get the light blue variable block, and click the FirstTimeJoining variable. Put that in the first slot of the equals block, and in the second, go to Logic again and get the True block and put that in the second equals slot and turn it to false. 

Then, for Do, go to the custom procedures again and get "Set FirstTimeJoining to:" then out that under Do, and put another True in there. Keep it as true.

Then, you get the summon structure procedure block and summon the structure you want. 

Too complex aswell. This is better https://mcreator.net/forum/63116/how-can-i-create-structure-only-genera…