Now that the NDA has been broken for a while, I have had Bannerlord alpha / beta access for a few months; at some point I did a deep dive of all of the available files and while I didn't find much, I did find some cool stuff. All below is what I have
assumed from what I have found, and I could be entirely incorrect.
Such as:
There is a command line similar to most professional game engines.
There are a couple things we can infer from these three images. The first image shows that the key to activate it is tilde, which seems to be common among a lot of games. The second image shows us that there is an in-game command line, which we can assume is used for live testing of changes and debug settings. The third image shows a live console of the game, and basically a modder's dream - being able to track where and what crashes a game, or any issues that arise. With all of this, it can be assumed that changes can be made and the game can be reloaded quickly to allow for easier modding in general. Currently, we have to change something, recompile and then open the whole game up again. These images alone give me a lot of hope for the accessibility of modding Bannerlord.
This is an example of how the map editor panel looks, or at least part of it. I'm not a mapper, so I don't know if there's anything truly mindblowing here. At the bottom, you can see 'Scripts', inferring that we can create custom scripts to put on maps as entities (I think). Not much else stands out to me. Also in this album is how code "looks". This idiot is using NP++, when he should I believe be using Visual Studio for c#.
You can create entity prefabs, meaning you can combine different objects or effects into one group and use that group instead of remaking a set of objects over and over. This saves a ton of time all over the place, as it means mappers don't have to re-do their work over and over if they wish to duplicate it. Assumedly, you can do prefabs for more than just mapping. You can also manually adjust the LoD, which is super handy for those wanting to save FPS on their resource intensive maps. This image also shows the whole front end of the editor, or at least the main screen - you can see all of the buttons as the images that Horakti posted earlier. Really cool that the game has its own integrated, clean editor and playtesting environment.
This is how navmesh building operates.
These images can all be found in \Mount & Blade II Bannerlord - Beta\Tooltips\Images (I believe they were intended as tutorials for the developers, and accidentally left in). As far as I know, modding tools will most likely not be released until after Early Access, when the game is released. This is disappointing, but understandable. The most I can do now is prepare by learning c#, and practicing PBR. Sorry to take over your thread.