To load your custom maps created in MapEditor you can easily create a Venice Unleashed mod with the use of this tool
A tool that generates a level loader mod from MapEditor save files.
Download: Repository
Clone the repo outside your mods folder as this repository should not be confused with a Venice Unleashed mod. It generates a Venice Unleashed mod!
Instead clone it in e.g. Documents/Projects instead.
Save files generated with MapEditor can be placed in the in/map_saves folder. The files should have a .json extension, the file names themselves don't matter.
Once done with map modifications, simply run the generate.bat file. This will generate a new version of the mod. The mod can be found in the mods/rm-levelloader folder. Copy this folder to your Server/Admin/Mods folder and enable it in the ModList.txt.
The LevelLoaderGen generate.bat has support for different output paths, so you can set it up to directly copy the generated mod to your Server/Admin/Mods folder. To do this, make a copy of the existing generate.bat file and place it somewhere where you can find it back. After that you should make sure that the path to LevelLoaderGen is correct and add an extra flag like shown below:
@echo off
cd <path_to_rmlevelloader>
call ./LevelLoaderGen/bin/levelloader-gen rm-levelloader <current-level-loader-version> -i ./in -o "<path_to_documents_bf3>/Server/Admin/Mods"
pause