The debug console in Witcher 3 can be accessed via a mod at Nexusmods. There are a lot of commands available to add items, spawn monsters and to do other fun things. The information on this page is gathered from the comments on the mod-page and from my own research. Thought it would be convenient to gather the commands like this. You are welcome to contribute to this list.
Witcher 3: Fast Travels and World Changes
Now that the debug console in Witcher 3 can be accessed, it is time to have some fun with it 🙂 To portal to certain locations in the game use these commands.