It works, but its very user "hostile" to say the least. Ive played around with it, and noticed the following limitations:
- Do NOT include any of the most recent civilizations or city states in the map. The civs and city states from the vanilla game works, as do "Random".
- Do NOT include any of the most recent natural wonders. They will crash the map upon loading.
- The editor is VERY picky about what can be placed where. Certain natural wonders and many resources will only be ploppable on, lets say Plain Hills, or Flat Grassland without any Woods on it. Play around with it to find out where everything can be placed.
In order to actually play the map, I followed the steps explained in the video below, and Im currently playing my own custom huge map with pre defined starting positions and it works perfectly.
It's a little more complicated than that.
You can use all civilizations and city states, including the latest ones. I have no problems with them. You must, however, observe certain rules for using them. E.g., city states need to be at least six plots apart from each other and they need enough space to deploy their starting units. They also need enough food near them to facilitate starting population. If you fail to provide that, the map will load but you will not be able to finish a turn.
Furthermore, you need to manually place all city state starting locations and either set them as "player starting location - player name (eg Brussels)" or you need to set them all as "random ai player - city state civilization level". It works with combinations of these alternatives but there are more hidden mechanics that can screw you over after an hour of working with a map, and I wouldn't advise to mix fixed and random starting locations for city states. You also need to match city state number in game's setting with the number of random locations or it may cause a crash.
Natural wonders work. All of them. The thing is that they require strongly specified conditions to be located and there's also a hard limit for natural wonders. If you add a 6th and a 7th natural wonder, the no.1 and no.2 natural wonders will be removed. You will not know which one are these until a map is loaded. If you screw around by placing and removing a natural wonder 30 times, it will be a lotery when you actually start the game. The most problematic are 2-4 tiles large natural wonders. The green indicator for placement will work only for a single plot but all required plots need to wonder-friendly for it to be properly placed. You need to discover rules governing placement of natural wonders. I managed to do it only with a few before I gave up worldbuilder and the whole game.
There are also many quirks of the unofficial after all tool. Plots around lakes have a hidden "lake shore" modifier. You won't be able to do certain things after removing the lake but you'll be able to build cliffs around a mountain if you please. Also, natural wonders cannot be adjacent to simply anything. There are rules about terrain type and terrain features in their neighborhood. Sometimes, you will be able to place a natural wonder when such features are already placed but it will likely cause a crash.
The biggest problem with worldbuilder is that the tool is governed by a myriad of hidden rules and you don't really know what you are doing most of the time.
And I wasn't able to properly disable barbarians...
