First of, from what I've seen so far the mod seems amazing, great work. Now my issue; I get a massive lag of around half a second whenever I enter the edit-mode. I haven't profiled but it's probably because the mod recreates the surface every time. You could keep the surfaces intact instead of throwing them out every time the player leaves them. You could clear the entities but keep the surface itself in reserve, maybe maintain a list of them and assign a free one every time a player requests editing.

...what?

Ok I was tired when I wrote that, I'll try again. Every time I click the composite combinator to edit it, I get a half second lag before the game lets me edit the combinator, which is really annoying.

I think this is because you create and prepare the surface where the editing takes place every time. And then when the player is done editing the composite combinator you delete it. Instead of deleting it you could just leave the editing surface intact and only remove the combinators, that way when the player wants to edit another composite combinator you don't have to create another surface because you still have one. So I'd only get my half-second lag the first time I want to edit a combinator.

Of course it's a bit more complicated than that because multiplayer is a thing, but that shouldn't be insurmountable.

Does anybody know if it's the creating of surfaces that causes that lag?

Haven't checked in detail but if it's creating a surface and the map generator starts generating chunks then that gives a big cpu spike and halts the game a bit. I have that effect with other mods that create surfaces myself.

The suggestion to keep the surface is sound but tricky if you want to only have a few surfaces and always use the next free one. Like when 2 players try to enter a different combinator on the same tick.

It is created with a very small number of chunks, so generation shouldn't be an issue.

Also this would be a problem in multiplayer if more than one combinator is being edited at the same time.