It was promised by the developers and finally released. TaleWorlds Entertainment, developers of Mount & Blade 2: Bannerlord, have made available the official tool for modding of their game.
You can download the kit from the tool list of Steam as long as you have the game installed and updated. With the kit you will have access to a scene editor with a large assortment of tools that will allow you to edit, import and export terrain, insert new objects, edit paths and more. There are also a ton of resource editors that allow you to edit anything from textures to character skeletons and so on.
Even without the official tools, the Bannerlord community still got busy, filling the pages with Nexus Mod. With this tool surely the mod volume will only increase considerably.