Is there some kind of map editor that allows to create custom scenarios for this game?

Creating own stuff is half of the fun for myself. Thus I would highly appreciate some kind of software that enables us to easily create new maps.

Same here. This would be great fun and i think it would not take much programming effort. (maybe even an official tool, made by FFG?)

I just recently used Hexographer to create a map for a scenario; it's not designed for BoW obviously, but it worked well for me to essentially "record" an image of the map I made for the scenario. I just put numbers into the hexes where units start, then described what units go in each number, and the rest of the details for the scenario I typed up, all in Word. You can save the map as an image, which I then just pasted in the Word file.

http://www.hexographer.com/

Good luck!

Great! Yes, this should work. It even has bridges!

Thank you very much!