Explain your idea

I think that there should be a creative multiblock autobuilder. I also can not figure out how to build the excavator because it shows the engine and bucket wheel seperately so i can not figure out where to attach the two so i think the entry should be updated.

I see no reason in adding this, since structure blocks cover this.
The structure files in turn are found on this very github.

where are they i am new to this github

o wait i just discovered it in /place

but there should be a command for the list of multiblocks

This does already exist. All multiblocks are vanilla structure files, so you can just give yourself a vanilla structure block, then load immersiveengineering:multiblocks/crusher for example. Perhaps to make it easier to find there could be a /command added which gives a list of multiblocks, then gives you a structure block with NBT preset for loading.

can a command be added for the list of multiblocks

Here: https://github.com/BluSunrize/ImmersiveEngineering/tree/1.19.2/src/main/resources/data/immersiveengineering/structures/multiblocks

Also, vanilla Minecraft has autocompletion on its place command. It's genuinely this easy:

As a side note, this functionality does exist in the Projector from Immersive Petroleum. That is an extra mod though, which is probably not a preferable option, and the Projector also doesn't quite fit the theme of Immersive Engineering in my opinion.

thx