Here is some information on how this works. The settings in serverconfig.xml tell the server where to look to find the world, and you *MUST* have the directory structure to match. I've done it this way for years, and A20 has NOT changed how this works.
In serverconfig.xml you find two critical settings, GameWorld and GameName. Normally, GameWorld is set to RWG, but you can actually use whatever you want if the world already exists. If you use RWG, the server will generate a random world name, such as Seciwe County, etc., and then generate the world if it doesn't already exist. This name, Seciwe County, West Yapai County, Piveka Valley, etc., is based on the seed and you have no control over this. You can just use this, or if you want more control over your world directories, you don't have to use RWG but can use anything you want.
Please not that the comments below assume the world has already been generated, and you know where to find both the world and the template files - and you know what I mean by "world" and "template" files, as they are two different sets of files in two different directories.
Let's assume you have this in serverconfig.xml:
<property name="GameWorld" value="RWG"/>
<property name="GameName" value="BorkLand"/>
If you do this, the template name and first level world name will be automatically generated by the server based on your seed and you have no control over this. So let's assume your seed causes the server to generate the world name "West Yapai County". Your directory structure will look like this:
saved_worlds/West Yapai County/BorkLand/
saved_worlds/GeneratedWorlds/West Yapai County/
If we don't like letting the server name our worlds, lets not use RWG for GameWorld, and instead use the following:
<property name="GameWorld" value="GameWorld"/>
<property name="GameName" value="GameName"/>
(I set GameWorld to "GameWorld", likewise GameName, just to illustrate how this works, you can put anything you want there)
The world goes here:
saved_worlds/GameWorld/GameName/
And the template goes here
saved_worlds/GeneratedWorlds/GameWorld/
I frequently set both GameWorld and GameName to the same values:
<property name="GameWorld" value="My7dWorld"/>
<property name="GameName" value="My7dWorld"/>
In which case you need this directory structure:
saved_worlds/My7dWorld/My7dWorld/ (actual world files)
saved_worlds/GeneratedWorlds/My7dWorld/ (template files)
Do you see how the directory structure works? GameWorld is the first level directory name, and GameName is the second level for where the world files exist. GameWorld is used for the template files under GeneratedWorlds.
I've done it like this for years, and my testing with A20 indicates that nothing has changed in this respect. It's a simple concept once you wrap your brain around how this works, but the server has zero tolerance for you not getting it exactly right.
WARNING: If you don't have the world already created, and you put anything other than RWG (or NAVEZGANE) in GameWorld, the server will expect the directories to be there, and will throw an error. It will NOT generate the world. To generate the world on the server, you have to put RWG into GameWorld. Once the world is generated, you can then change this and move the world to whatever directory you want. Or just leave it there. Your choice.